Because of high interest rates, and unfortunate but necessary late fees, I owe nearly two times the cars market value. Should I attempt repairs and continue to pay for a few more years, or use it as a trade in?
Well cars don't tend to go up in value. The money you spend on them you'll never see again!
With this in mind I'd do one of two things:
#1 Do the most basic of repairs and continue to drive it. (OR)
#2 Do the most basic of repairs and sell it ASAP and get something more basic.