Hi Ten steel frames are the very bottom of the market. Cromoly frames are much better. This bike would have to be really cheap to be worth fixing. It would help if you had a donor bike (another cheap find) where you could "borrow" the wheel you need. Does it have alloy rims (the Grand Prix came with steel rims, but that was a common upgrade people did to that era bike).
If you don't already own it, I personally would not buy it. If you own it, I would consider selling it and using the funds to get a better bike.
Araya R200 - Apollo Custom Sport - Specialized StumpJumper
I do own it, but it was donated so the cost was nil. I got a donor bike with a straighter looking rear wheel, but it's a shimano hub 5 gear, and not suntour type 6, so I think I'd have to unlace and switch the rims to use it.