There is a small gauge or a plastic blank to the left of the radio. Snap it out and unbolt the radio. The first time you pull the radio, you may have to remove the glove box and reach behind the radio to release it. I think, however, it will just pull out on an '89.

That radio is not worth fixing.

I nursed along the radios in the '87 and the '91 for years because I wanted the dash to look original. When I finally replaced them with low end Sonys, the sound was significantly better and they looked good. Why did I waste my time with those piece of junk original radios?

I got kits at the radio install shop at Best Buy. One kit made the wiring plug-and-play, even bypassing the amp in the '91 that had failed. The other kit fit the dash to make the radio fit smoothly and fill the odd-shaped hole in the dash.