I checked GM Service Information but your vehicle is too old and they purged all data for it except bulletins. I did find a book on the rebuild process which should work just fine for you if you're willing to crack it open.
Amazon product ASIN B012GWFQHG
If you've never rebuilt an auto trans before just be sure to take your time, get containers to separate components and label them. Be sure to make sure all parts are super clean, use shop air and a dial indicator gauge to check your clutch pack travel before assembly etc. Also be sure to dip your friction discs in proper ATF after you perform the clutch pack travel measurement. Last but not least get assembly goo and make sure any of the check balls are in their proper bores, ALL accounted for. Consider a new valve body as well or at least giving it a proper cleaning and replacing any solenoids.