Have both the Kirban and Helm manuals. The Helm is the dealer's shop manual and covers all 1986 Buick products. It includes all the wiring harnass schematics with trouble shooting steps etc. along with service procedures for just about everything on the car. Cost of the Helm manuals is around $85 and it is 32 pounds of paper! Also it will take a considerable amount of time to "update." Three updates plus a suplement must be applied. Lots of pages to replace. BTW it is still available new but almost impossible to find and expensive used. If you are serious about doing most of your own work on the car, I'd get the Helm manuals. Just my .02