Has anyone tried fixing one? I looked online and found some old videos but none were specific. Could I get the spare parts at a local electronics store or should I go to Radioshack or similar

 

Not sure I understand the question.

 

Usually I order my parts from www.digikey.com or www.mouser.com

I've fixed many amps 70% of the time people blow out the switching power supply transistors. With out the proper tools though you are just guessing.

You really need access to an oscilliscope to properly diagnose and repair amplifiers.
You could take a wild shot in the dark and replace the power supply transistors. It would cost you probably about $15-20.

If you open you amplifier and snap a photo I could tell you which parts are the power supply transistors.
But again this is a guessing game without the proper diagnostic tools.

 

If you got just a single channel out, the most likely it's the cap and the resistors and transistor for that channel. Do you get any sound at all? If you still get sounds but super distorted then that's it. Take off the burn parts and get the location numbers. If you have an old MTX amp, email them and they'll tell you the specs for the parts.