TSC did mine along with a b&t barrel swap and my sbr engraving. If I was going to do it again I'd hand the gun right back to Mike. I didn't have mine refinished but if you want it swapped to say mp5k then chances are you will want the parts installed after the refinish.
I'd just ask whoever you are thinking of sending the gun to for the barrel swap. They might just say buy the kit and send it to them with the barrel and gun.