First off I would like to say welcome
And yes you can wire up an amp. You need to go buy an LOC(Line output converter). You can buy one of these at your local best but or circuit city. Should cost around $30-$40. You will tap into your rear speaker wires behind the stereo. This will give you your RCA's. As for the Turn on, you can just run a wire to a fuse that is in use when the car is on, such as gauges(may work not sure), but something like that. The rest of the amp wiring is normal.
Hope that helps. Rep is always nice.