The girdle has DETAILED installation instructions included. (providing you bought a new one from RJC) If not, download the instructions from someone that does. If your shop doesn't know what they are doing, find another shop. It's not rocket science, but the details will kill the engine if not followed.
As stated earlier, girdles do not use a gasket between the girdle and block, just high grade silicone (the "right stuff") and the block and girdle must be true and flat. There needs to be a .005" gap aftrer torquing the main studs. Then torque the pan studs, then line hone the block to specs. The main caps need to be milled flat and cut to allow the installation of the girdle and have material to line hone to size. Labor instensive, for sure.