Platter warp on my ATLP120?

Hey everyone! Lately Ive been noticing that my tonearm is bouncing up and down way more then it should. Thought that maybe it was just uneven records. But then I noticed that its the whole platter; maybe a warped platter or platter wobble? Im still kind of new to the Vinyl world so I don't know all the terminology per-se. Anyway, its way outside its warranty, so I have to try and fix this thing myself. SO, here is the real question:

A) Should I try and take the platter off and put it back on to see if maybe it just wasn't on properly?

B) If so, how the heck do you take the platter off on the 120?!

Thanks for the help guys!

 

I should also note that, Im assuming as a result of the platter issues, songs are playing unnoticeably slower. You couldn't tell just by listening, however when I record a track, and then compare it to a digital version, I notice that the vinyl is playing ever so slightly slower. Don't know if this info would be of any use to you guys.