I just fixed up my 89 and have some notes:
1. It's really easy to get this thing out of the car. On the driver's side there are 2 7mm screws along the bottom of the dash to the right of the steering wheel. If you unscrew those you will be able to pull down the bracket that holds the module. You don't have to take anything else off.
2. After you take it apart you can just bend a piece of .080 weed wacker line into a circle and put that between the metal disc and the 4-prong retaining ring.
Then just put it all back together and you're done. I tried using an o-ring before the weed wacker line and I don't think it was as loud.