I highly doubt that if you go back there afterwards that they will refund your money. If you contact them ahead of time, shops will very often stand behind their work and fix the problem. But they won't let someone else do the work, then fork out the bucks for it.
But I can understand everyone is in a different situation, and sometimes that drives the paths you can take. But if it were me, I would make every attempt to contact the garage that did the initial install and talk to them before anyone else does any work to the car.