Fashion yourself a blunt L-shaped hook from something like a 3" nail. Open the tailgate. Clean your hands. Use the flat of your hands to stretch the vinyl roof fabric a bit toward one corner. Insert the hook above the now loosened outer edge and simply pull out the plastic retaining edge. The plastic edge simply sits in a metal lip that goes all the way around the roof. Once you've got a grip you can easily pull away a corner section for access to the wiring and hinge retaining bolts. A warm area makes the vinyl easier to work with.

If you need to remove a hinge (and you will) then support the tailgate with something like a stepladder and put some padding between the open tailgate and the roof to protect the paint. Hinge removal is a bit fiddly the first time you do it -just proceed carefully and have a wire coat hanger handy for fishing.

You can put in a replacement wire harness (available from Volvo and ipd) or make a spliced repair. Red/black test lead wire (avail at Radio Shack) makes a good flexible splice through the hinge area (regular stranded copper wire will break again fairly quickly). You might as well do all the other wires in that hinge while you're in there -they'll be going sooner or later. Also check the small black ground wire riveted between the hinge sections.

See the FAQ and archives if you need more tips.