Unfortunately, can't help you with install advice, because mine was worked in as part of the deal.
What I will tell you to watch out for, is, if the detachable rack does not have the "ledge" that your wiring sits on like that on your stock fixed rack, you'll need to find a way to keep the wiring off your rear fender when your detachable tour-pak is on the bike.
I'm getting my fender replaced as a result of pitting/marring caused by the wires (specifically, plugs) sitting on the fender after a long trip. Had I done the install myself, I'd have eaten the cost of the replacement, or just had to live with a damaged fender. Fortunately I've got a great service department and a super service manager.
The "fix" for this was addressed in another forum I saw after the damage was done to mine. No pictures were provided and to me, the directions were vague. Can't say exactly what was done, but had something to do with heating and forming plexiglass, attaching that plexiglass to the bottom of the rack and then resting the wires in that. Have no idea how thick the plexiglass was, or how it was formed. Propane torch, heat gun, I don't know. Might give the plexiglass thing a try. Here's what I will tell you. Don't think for a minute those plugs sitting on your fender for even a short ride won't damage your paint; they will.