2002 Cadillac DTS RIGHT DOOR EXTERIOR MIRROR

I broke the right door side view mirror, but the mirror frame is OK. I would like to get a salvage mirror and just replace the "guts" of my present frame and the broken mirror. My mirror has seat memory with it. I can separate the 2-part control box that the mirror mounts onto and which includes the plastic sprockets, etc. Which make the mirror adjust. All that is broken is the front part of the control box casing, which is what the mirror snaps onto, and the mirror. The wires that come thru the door come into the back half of the casing, so replacing the front half of the control box casing avoids upsetting the wires. Should I just replace the front part of the casing with the salvage part, or should I replace the entire contol box. If I only replace the front part of the casing, I may have a problem making it waterproof again. It looks like replacing the entire control box will require re-routing the wiring harness thru the door hinge area, unless I cut the wires and solder on the salvage part. Where does that harness plug in when it gets into the passenger compartment? I removed a plate under the glove compartment and it appeared that it may go under the carpet. Which alternative should I try?