03 GM Truck Relay

I have recently purchased a 2003 GMC Z71 ext. cab, and want to start my system.  I have heard about a relay that I need to use with my stock deck so that I'm able to listen to my system when the truck is not in the run position.  I am using my stock deck because I don't want to loose my chimes which go through the deck now and out the door speakers.  I have the speaker wire to RCA adapters but don't know much about the relay.  It seems every time I install a system I am using an after market deck but in this case I need the chimes and the steering wheel controls as well.  Can anyone help me?

Thanks

Seth

I'm not for sure on how to wire the turn on wire for your amps so they stay on with the radio but... If you wanted to add a aftermarket radio and keep the chimes you can get a reloaction harness and just hide the radio under the seat or something then put the new one in its place. Then if you want to be able to use the stearing wheel controls there is a device that interpets the commands from them and send them out as a ir singal - catch is that ur new radio must be able to be used with a remote.