I vote refinance. This could cut the interest owed overall. Make larger payments with the refi to knock back to the actual value of the trade in. Plus, with the refi, most likely will have a lower payment so should cash be an issue, at least you can make min payment. Don't worry about having another 24+ months tacked on, all that matters is that you pay it down faster.
Of course if your CS rose since first purchase your APR will be lower too.
Once youre above water or have the cash difference for the value of the trade in vs what is still owed, trade that sucker in. Carmax is a halfway decent group but I suggest shopping for a loan first if you need one at your bank or credit union. Carmax will value your trade in so you know what you're dealing with better than Kelly BB unless you want to sell on your own.
Imo never trade in when underwater bc like a bad one night stand, that stuff comes back to haunt you.
