Sorry to hear about the water damage to your amp, that's a tough one. I had a similar issue a while back with my car stereo after some unexpected rain leaked in. It turned out only the left side speakers were working properly. After checking everything, I found out the amp was fried too.Buying a used amp sounds like a good plan, but before you do, maybe check the connections thoroughly once more just to rule out any loose wires or corrosion.As for mold remediation, when I had water issues at home, I called in a mold remediation san diego. They were quick to respond and did a fantastic job cleaning up. Just make sure whoever you choose is reputable, like the folks at that San Diego company you mentioned.