How much would my 1982 mustang worth?

Actually...depending on what kind of shape it's in it could fetch a lot. I'm not familiar with a specific 302 Boss model, but the 302 (5.0) GT model can go for about 7k in excellent shape, 13k in like new condition.

The down side is that 1980-1987 were pretty bad years for Ford and most cars and trucks were notoriously unreliable. Getting someone to actually buy it at those prices...all I can say is good luck.

It would depend on the condition of the car and the documents that support it. The 79-93 foxbody plateform has a pretty good following. I'd try out some foxbody mustang forums and ask some of the guys about it.