2001 GMC heater core removal, DONE!

Got the soggy thing out, there are 4 bolts and 1 nut on the engine side of the firewall to take off. 1 bolt is inside the AC cowl under a heat sensor lid, (3 screws), 1 on the right of the cowl and 2 under it (couldn't figure how to get to those and they broke the plastic core cover where they attach when I bent it do to get the core out). The guy at Walts said the ground between engine and firewall wasn't very good and caused electrolisist? to make it leak, the truck only has 68K on it. They wanted $1100 for the job, 7 hours of labor for me but now I know my truck inside and ?. Now it's time to put a bunch of screws back were they belong.
Gene

ok, I just got the truck (69k miles on it) back from the shop due to the MAS and it running like crap when it shifted, the mech told me the coolant (dex? guaranteed for 100K miles) was exposed to air through the radiator cap and thickened up and got weak and rusted everything it touched, heater core that I just replace, intake Man Gasket is leaking,water pump is leaking and radiator will be next to go. Sound familiar? Factory defect? although they wont claim it, I will never buy another GMC product again, Toyota here I come