Not sure what year you are looking for but, do not order the 1991 Service Manual from Helm, it is a photocopy in a binder. Order a 1993, it will be completely applicable and come is a perfect bound book. Additionally there is a Electrical Troubleshooting Manual and a Body Repair Manual.
I have found the Service Manual to cover 99% of what is required. Rarely do I need to spend too much time in the ETM.
HTH,
LarryB