If that doesn't work, please let me know. (Message me if I don't answer the thread.)
I have a handful of Delco radio manuals, including several of the Fiero radios. I can scan and email what I have.
Edit - I searched the part number, and realized that this is the most basic cassette player that was available.
I don't think I have manuals for that particular radio, but I will still have a look.
(For what it's worth, I fixed one of the "nicer" Delco radios that had tuner issues. The display would stay on one thing, but the frequency would "scan" up through the band.
It was caused by a poor solder connection on the "VCO steering line". The quick and dirty fix for Delco radios is to re-flow every solder connection in sight. It's a bit time consuming, but I have found great success doing this.)
[This message has been edited by Raydar (edited 04-09-2020).]