You asked lots of questions that have very expansive answers. Because I have some time restraints today I kept my answers fairly basic.

Is it a college education in the social media field?
Though I haven’t checked, I sincerely doubt it since it’s a relatively new and ever changing.

How do you know that someone is legit?
This is a very good question and many articles have been written on it. Google “how to choose seo company”

What other facets does a person need to know…. to call themselves an expert
SEO is a ever expanding skill set and in my opinion isn’t done by one job title.

1. Designer: SEO starts with planning the design interface. Looking good + user experience + functionality. Content and backlink planning should start here, but may or may not be done by the Designer. 
2. Developer: html/css/javascript the site needs to be build so not just humans understand the structure and content flow but so do robots indexing the site.  The pages optimized so they load as fast as possible. This is a pretty simplistic explanation, but this expresses the basic idea
   
3. Business Owner: Owners need to understand how to add content to their site that continues the plan laid out in step 1.
4. Social Media – multiple online presences are now a integral part of SEO. Setting up these accounts, optimizing them and then having an editorial calendar for posting to them (as well as your website) is very important to Social Media Marketing as well as overall SEO.

lol, I guess I would like to be able to call myself a “social media expert,” but I feel like I would need to take a class to become certified. 
I don’t know of any classes like this that are part of a collegiate organization, but there are experts out there that offer training. You can check out http://socialmediamanagerschool.com/ Andrea Vahl and Phyllis Khare are proven Social Media experts and I’m sure put out a fine course.  I took their free intro webinar and learned a few things I wasn’t already aware of. I’d of taken the course, but I try and use my educational budget for training that is more in my wheelhouse as a developer. 

In your opinion, which ones of these platforms are the most important.
*Facebook
*Wordpress
*Twitter
*Linkedin
& all of the others
I’d say it depends on a lot of things like who your target audience is. Don’t forget Google+

I know I didn’t address all your questions, but hopefully it was enough to get you started, and others I’m sure will chime in.  

Cheers
Jules

@kim-olive Wordpress is a great platform, but it doesn’t help get people form your facebook page to your website in it’s self.  Creating content (blog posts) and sharing it yourself as well as encouraging others to share it on facebook and other social media is a big part of how you do that. Wordpress enables you to add and manage content on your website easier.

Choosing a developer that understands how to integrate social media into your site is smart, but you need to learn about (or hire someone who does) social media and how to use it as an effective marketing tool. 

You found Social Media Examinar, that’s a great start. This site has lots of great info to get you started and keep you up-to-date on social media trends. You can also check out the facebook pages below.

https://www.facebook.com/AmyPorterfield 
https://www.facebook.com/GrandmaMaryShow 
https://www.facebook.com/smexaminer 
https://www.facebook.com/marismith 

i would  say  GO FOR IT….  and  be humble  in  your   portfolio…..  you wouldnt  be  claiming  everything….  people  want  you  for  some  great  reasons …i would never  go for a partnership…..   so many  reasons…

to your  questions….i start with buyer beware….. as an outsider i would   beware  but i would  look at  the   providers   testimonials  and  hopefully   referrals  from  people i  know…. 

in  watching the person i would  really look at the  depth of  their talk…are  they   advising  the great  general   first  paragraph of   the  basic  google    info, that  basic   stuff that  we all  read over and over?  or  can  they absorb  the  customers actual  question or   need  ? and  dig  down a little  deeper, custom replies…?

lol…kim  , the   best  seo  guy i  know thinks  facebook  is  minor and a passing   fad…. he  doesnt  get it at all….but hes  really  smart; on   seo….and  blogs…i was on a forum  with him once for  quite a while….    you wouldnt want a person like that if  facebook is  important…………

i respect when they  say  im  good at  facebook or you tube   ~~~  but  limited on   pinterest or  wordpress or ~~~…i wouldnt  expect  anyone to  be up on everything…

as a  business owner,almost  all  brick and mortar…. facebook is   first  by  huge margin….  then pinterest….i dont use the others… i  do   know  and need to know   some about   seo…… and   also  need to  know  how to   work   a  good   email   database and   plot….  so  presenting  those  2  might  be  good too to have in  your  social media   offering…

seems  to me  its a lot like my field (antiques}    anyone can  call themselves an expert, and  they do!!!

@kim-olive  From personal experience, I started using Social Media when I was first introduced to it by Mari Smith during a webinar.  Within 3 months, I experienced a lot more business and referrals. But as Social Media was growing so fast with so many changes, I could hardly keep up.  I invested some money in training to get “certifications” as a Social Media Marketing Specialist and Internet Marketing Specialist through VA Classroom (since I was a Virtual Assistant).  Craig Cannings at VA Classroom was an Internet Marketer for years and transitioned into teaching to VA’s around the world.  He saw the need for “certifications” in the marketplace and provides comprehensive training including an exam at the end.  If you don’t pass, you go back and do it again and get retested.  You may wonder how effective it is?  Well, I had an alliance, a VA who paid one of our colleges over $5000 for a comprehensive course in same and had to call me to get answers on “how to” in Social Media.  I couldn’t believe that the questions she asked me hadn’t been taught to her.  AND, if VA’s around the globe are not social media saavy, they have referred their clients to me simply because they know how good the VA Classroom courses are.  In fact, those “certifications”: have backed up my knowledge and most VA’s won’t hire someone for social media unless they have those certifications.

Here is an article the local newspaper did about my page,
https://www.facebook.com/fortbenningareaguide

http://www.ledger-enquirer.com/2012/09/09/2195934/5-questions-with-kim-olive-building.html