Can I trust this guy?

I'm looking for someone who really knows what they are talking about. I traded a guy my amp and got home and hooked the new one up. It takes 4 25 fuses. I put 30s. The amp got very hot in a few seconds and blew my 80 power wire fuse. Then a 50. So I went and got my amp back. Now he told me he put 40s in it with a 200 in line fuse and it worked. he told me "the power resistors were bad" and he payed and got it fixed. Would this be the problem? And would it cost 20 dollars to get fixed?