You may want to look at Marketo university here: http://learnadmin.marketo.com/searchresults.aspx?q=building%20landing%20pages&at=T&ty=ML.BASE.DV.SearchContains
There are some excellent online and free courses.
From what you've written I think you are looking for the page to change dynamically depending on what link they click?
I believe you can do this using the query string and then a token on the LP based on the query string used. However, if you're still new to Marketo I'd suggest making different LP's per source that you want to promote, and then use one form on all LPs and then the Smart campaign to track who fills out he form on what pages.
Hope that makes sense?
This might not how others would recommend to do it, but I'd use something like AddThis or Shareaholic. Both services allow you to add a bar across the top of your screen with custom messaging based on where your visitors' referral type. The basic service is free; I'm not sure if this particular functionality is paid. It's probably a little more down-and-dirty than what you're looking for, but it's been useful to me! And there's tracking, too