Unless the seal is woefully toast, you should be able to get Prestone Power steering fluid with Stop Leak. It helps to rejuvenate rubber seals.

Brush the stuff on liberally on as much of the rubber if you can, ie, if you can take the seal out so much the better, but you might not have to. Brush the stuff on, leave it on for about an hour or so to be absorbed in, then wipe it off with just a paper towel or rag. You don't want to use any chemicals whatsover. Just wipe off the excess.

Keep the sunroof open overnight if you have a garage or if it's not going to rain, and then use it normally, but do open/close it a few times over the first few days to make sure the rubber seal doesn't stick to the roof.

I just saved you $176 and a lot of work having to take the seal out.

jeff 1991 300d