Cadillac Repair: 1997 Cadillac seville w/4.6, blown head gaskets, cadillac seville

Question
I have one in my shop that is giving the following codes PO300 PO603 B1552 B2419 B1318 C 1255 B1552 B 2560. This is my first Caddie. I am in the automotive tech school with graduation in June. I needed a career change and this is something I like to do.  If school was in session I have access to a TECH 2 at school but that is next week. Also this vehicle was brought to me with aa overheating problem. It blows water out of the overflow tank after shutting off the engine. I suspect blown head gaskets. Any help would be greatly appreciated. Thanks Blaine

Answer
Your learning. You are CORRECT on your diagnosis of blown head gaskets which is very common on this engine.

I would not worry about the codes until you get the head gaskets replaced.

NOTE:

You MUST drill out the original head gasket bolt holes and install inserts and or larger bolts  BEFORE you replace the gaskets.