car over heated I pulled over right away. I took it to the shop they said I need

I would start by towing the car to another shop. Have them perform a block test on the cooling system to detect combustion fumes in the coolant. If that checks negative, have them pull a vacuum on the cooling system and fill that way. The head gaskets on the 6 cylinder cars doesn't suffer overheating well and may have blown. The shop will need special tools to retime the engine properly if the head has to come off. Hope this helps some.