I would check in either a factory service manual for your vehicle, or a Chilton type manual. If you don't have either most public libraries have Chilton manuals.
Looking in my factory service manual for a 1989 Chevy Celebrity I found no reference to an accessory relay.
On some cars there is a sticker in the engine compartment with a belt diagram.
You can find fuse block diagrams for your 1989 Chevy Celebrity in either a factory service manual, Chilton manual or Haynes manual. If you don't have a manual your local library may have a Chilton or Haynes.
Prices tend to vary with suppliers, there does not seem to be a standard price. When I need parts for my Chevy Celebrity I survey the local sources and buy the best deal I find.
Looking in my 1989 Chevy Celebrity manual I find a park relay inside the wiper motor but no reference to an external wiper relay. There is a fuse on the fuse block.
You can find the wiring diagrams for a Chevy Celebrity in either a factory service manual or either a Chilton or Haynes manual.
The cops around here won't let me find out. I did try though. btw, anyone know a good lawyer? These guys have no sense of humor.
Chilton manuals don't include wiring diagrams, but the Hayne's manuals do. Also, if you have a well stocked public library, check the manuals there.
try autozone.com
You can find them here->http://www.boxwrench.net/specs/chevy_sb.htm
where do I find it
For the fuse block layout check in either a factory service manual, a Chilton manual or a Haynes manual. If you don't have one the Chilton or Haynes manuals are often available at a library.