Here is what my 1990 repair manual says about removing the parking brake cable. Judging from the pictures it looks to be the same as the 1989. steps 4 - 8
How the Teves ABS system works
This is a good video that I found on YouTube that gives a good description of how the Teves MK-II ABS system works. It is on a Chrysler vehicle but it is the same ABS system that is used on the Buick Reatta. You can learn a lot from it.