MiniFtops can be bought in for with FTPs.
As others have mentioned, if you buyin with FTPs you won't get a refund in cash for unregistering.
I've never heard of one being able to sell one's FTPs?? Anyone do this regularly? It sounds a bit odd as they're not transferable so are of no value to anyone else.
5,000 FTPs sounds like alot but when you go shopping with them (be it satellites/tournaments/ or stuff from FT store) it really doesn't have alot of value (but hey, it's 'free'!). I'd consider using them to try to win even more FTPs. Depending on where your own personal strengths lay, I'd either play the 500FTP super satellite MTT to the $750K (500FTP >> 2,500FTP). It usually runs daily at ~20:55 (<< pretty sure that's when it is). OR, if you're good at SNG's, there are a number of FTP satellites in the SNG lobby. Just check through them and see what interests you.