Welcome to GasGas and the site!!! I still love my '04!
The '07 seat is a lost cause I think. If you can't live with it I think some guys have switched to GUTS foam or the '08 foam. I'm sure another '07 rider will chime in.
I got use to the seat... doesn't bother me any more, look into getting the suspension plusher, that will make a huge difference in how well the bike works and how fast you want to go.
Harsh suspension was my only complaint about my 08