1) Since you say speakers, I doubt both are bad. Sounds like a plug or wire might be loose somewhere. If you do want to replace them, they have to come out from inside the car. Remove the lower seat cushion, then the back seat cushion and finally the rear decklid. They are screwed in from the top.
2) If your blower only works on high, the blower resistor needs to be replaced. Famous problem on these cars. Have had to replace it on 2 of my 3 GP's. If it is staying on when the key is off, there must be short somewhere. There are power wires that are always hot and some that are hot when the ignition is on. I would guess you have a short jumping one to the other somewhere.
3) See #2. The blower and heated seat should both come on only when the ignition is on.
4) Have a mechanic put a scanner on it and find out what the abs code is that is causing the light. I had an intermittent problem like that on my second GP that turned out to be a bad wheel speed sensor. It could be any one of the four wheels so a scanner is the best way to track it down. Also a common problem on these cars.
Good luck
