Re: cd changer
The CD Changer can be mounted in two places. The traditional place (where factory installed units go and where and auto guide will tell you) is on the lower left side of the trunk for the sedan. This is of course a low spot so when you fill the car, it could get knocked if things slide or be hidden when you want to change CDs.
I was told about putting it up at the top of the hood, right of the left trunk hinge. This allows it to be always accessible, if water runs it in won't get wet (just set it behind the lip of the trunk). Send my your e-mail and I'll get some pics of it.
The RCU is the amp/input controller. The in-dash unit only sends control signals to the RCU, the RCU actually makes the stereo work.