1999 Mercury Mystique stereo amp location

I attempted to "troll" the forums, bout was not succesful in finding a thread already dedicated to this, so I decided to make one.

My wifes car is a 1999 Mystique. Originally, when we got together it had a JVC aftermarket CD player that was installed from Circuit City, and since then, the JVC took its last breath. I purchased a new aftermarket stereo for her for a B-day gift this Sept, and it worked fine. eventually, we ran into minor problems with the car, and had to take it to a repair shop. While there, they left the hood partially opened, and as a result the battery died and was in need of a jump start to get it back up (the batter was also on last foot, and had dead cells, and has since been replaced)

The problem that we now have is this... Since the replacing of the dead battery, with a new battery, the radio has not made any sound. It turns on, and is fully functional otherwise, but tthere is no sound, and I know that theres a factory amp.

My question that Im hopeing to have answered, is could someone tell me the location (in detail please) of were abouts I could find the factory amp, and also if you think that it could be as simple as just needing to replace the fuse/fuse's in said amp, or if that could present a slightly more serious underlining problem.

Again, it worked just fine till after the replacement  of the new car battery.

Also, although slightly off subject, does anyone know if these can be purchased, and if so, how much aproximatly, so that if its needing replacing, i know how to go about it.

Thanks to anyone who can offer me insite, and help with this problem, and please feel free to also help "troublehoot" this with me.