Can I fix, or do I need to replace?

Yesterday I opened up my MPC 2500, to clean grime/dirt in between pads + check my rotary wheel, which was grinding up into the case a little bit. I had no problem taking the case off, because I followed a youtube tutorial. After I took the case off, I spinned the wheel and it worked much better. I also took the wheel off of its base (which is white). I noticed some sort of oil on that white piece, and inside my wheel, so i wiped it with a cloth. My wheel doesnt really work anymore, unless I push it in. Could the problem be because of that oil?

Thank's, Ruslanio