As I just did this in my '97, you need 5 wires to the amp. Battery + and -, remote turn on, and the L & R signal cables. Without those, no go. Your deck has a sub pre-out setting -- make sure that is enabled. And then of course, the speaker connections...
It's also a possibility that the pre-outs are malfunctioning? You should look into that as well.
As for a power switch to the amp -- use the remote turn on and wire the amp the "right" way -- you'll avoid issues and confusion down the road.
I ended up constructing a custom box/amp rack that mounts up on the passenger side fender well and takes the place of the body cover. It houses a 10'' diamond audio sub and an Alpine MRV-301 amp... the whole setup blends in with the body great, but I did lose the ability to have my passenger side 3rd row back there. I used the 3rd row brackets to bolt and secure the box.
Combine a single 10 with replacing the old door speakers and you'll end up with a sweet setup. I am totally happy with mine.