"When I put in a tape, all my tape player does is change sides and ejects."
The small drive belt (rubber band almost) in the cassette is broken. Mine does the same as yours. A rubber band will not work as it is to slick.
From: Kingsley Smith
I bought one replacement drive belt at a car audio store. Another at an appliance repair shop. I've done this to two Fieros now. Bring the original belt with you so they know what to get. Usually they "eyeball" the belt and pick one that's a little smaller than the one you brought in (because the original is stretched). Price: $5-$10.
From: Derik Voigt