I'vehad my hatch off a couple of times now, so I think I can provide a few tips:

Be sure to mark the position of the hinges onthe roof before you start. I used electrician's tape the last time I did it, and it worked well. It provided a little ridge I could but the rubber up against.

While the hatch is off, check the wiring harnesses for continuity and inspect the ground wires inside the hinges. My '90 had completely broken wires inside the harnesses, but no breaks in the covering, so it was not obvious at sight. Also, both ground wires in the hinges were broken. I drilled a small hole diagonally through the center "rib" of each hinge half (actually, as close to straight through as I could get, then tapped it to accept a small screw. I connected a sew ground wire to each screw, rather than trying to use the original connections or repair the wires.

If you replace the harnesses, be sure to keep the plastic covers on the connectors (ipd sells the harnesses, but the connector covers are not included). They can be removed by inserting a tiny flathead screwdriver from, I believe, the wire side, and depressing a little "tongue" on the metal connector. They snap onto the new connectors. Put them back on last! You can't thread the new harnesses with them in place (it's hard enough without them).

Rather than replacing the harnesses in the hinges, some people install grommets in the headliner and hatch, and run the harnesses through the interior, so that a few inches are showing. It doesn't look as good, but it means you're not bending the wires 90 degrees every time you open the hatch. Either way, be sure to seal up the holes the wires go through in the hatch and roof.

Be careful: the hatch is freakin' heavy! If it's not propped up well, it can really hurt your head. Best practice is to find two friends to help, but I've done it alone a few times with some 6' fence pickets to prop it up.

Good luck! It's a very straightforward, common-sense job, but it's a bit of a pain, due to the weight of the hatch and the difficulty of threading the harnesses.

-EdM.