After reading all the above comments on here, here is how I would handle it if it were me.
1-List the truck for sale NOW

2-Go talk to the loan provider and tell them your predicament and that the truck is for sale. Ask if you can sell it below the loan value and sign a note for the difference. If not, check into a home equity loan (heloc). Especially if the same provider holds your mortgage. Tell them you want to sell the truck below loan value and take out a heloc for the rest. Don't go crazy and take a ridiculously low number and owe too much on the heloc.

3-IF you have enough equity in your home to cover the entire loan value on the truck, get a heloc and pay off the truck THEN sell the truck immediately. You HAVE to do this part. Don't get caught up in having a paid off truck. Take the money you get from selling the truck and pay off the heloc. You HAVE to be disciplined on this part.

4-Don't get caught up in this again. Read some money management books/magazines. Get on a budget.

God luck.