Bad exhaust valves

Hi all, I was driving to work and my 01 prism started to lose power, idled very rough! I took it to the mech and he said I have 2 bad exhaust valves. The cost to fix it is $1100.00 which is way too much. I willing to do the work myself but have never tried this type of work. I have changed many a gaskets but wanted to know if someone here can give me some pointers.
TIA

Rather than trusting his diagnosis, perform another compression test yourself. If the cylinders with low compression are next to each other, it is more likely that the head gasket is leaking between those two cylinders rather than two valves suddenly burning at the same time. Buy a repair manual if you don't have one. RockAuto is the lowest cost that I know of for repair manuals.