its an easy fix most of the time, just replace the chip or chips. maybe a 100.00 if you can find a repair shop. it entials taking the thing completely apart and desoldering the part and popping a new one in. if the shop has all the parts its about a half hour to 45 minutes.
get a relay. anyone running more than 1 amp could benifit from that.
hook it up so your decks remote turn on the relay and that should ease your troubles.
sounds like your amp is putting out dc current to the speakers. hook up a multimeter to the audio output on the amp and see if voltage is coming out. if so your audio section has decided to die.
The least amount of eqipment you will need is;
a Multimeter capable of reading dc, and mesure resistance.
a soldering iron with a fine and a thick tip.
handtools and cutting pliers
99% of amp repairs can be done with those.