back lights

A good shop will start with a fair amount of time to dig into this problem, it could take 1/2 hour or 3 hours, depending on where the short is located. About 1-2 hours of diagnosis time to fault trace this is about right, but it depends entirely on the shop.

It takes time to find a short, it depends on how hard it is to find. You may just have a shorted rear light socket, which do fail from time to time.