You bought the car to drive it, but keeping the paint from looking like a sandblasted chalkboard is a whole different chore. Swirl marks and clear coat haze build up over the years, and a proper multi-stage paint correction is the only real fix when basic wax stops working. Doing this right before you list the car for sale pays off in photos, but dropping six hundred bucks in one go stings.
Timing matters here. Detailers get slammed in the spring when everyone wants a clean ride, so look for a soft spot in the calendar right after winter ends or late fall when they are hunting for work. Get your price locked down with the shop independently first, and sort out how you want to pay for the invoice after you shake hands on the final number.
Remember that the 0% intro APR for 15 months on purchases and balance transfers is a hard deadline, not free money. If you still have a remaining balance when those 15 months run out, standard interest kicks in on the whole original amount.