So what happens if you waste money buying mosfets and the amp doesn't work because of something else?
I think you fail to realize how painstaking and time consuming it is to fix an amp, especially having to replace all those mosfets. Just to replace the mosfets you have to pull the whole board out of the casing, desolder all the joints, insert new mosfets, then have to resolder all those joints.
You can send the amp in to kicker, they will go through the amp and determine how much it will cost to fix it. They will call you with the repair price and ask if you WANT to get the amp fixed. If it IS too much money, then just have them send the amp back.