recall and blown head help

I have a 2001 Grand Prix GT with the 3800 enigine, with just under 36000 miles on the engine. I recently had a the coolant light randomly come on and after topping off the tank, and that not solving the prolblem, I open up the radiator. Not only was the wonderful funky sludge from the dexcool present, there was also a stop-leak plug wedge under my radiator cap, below the overflow hose. I was originally told this was a failed attempt at a recall in spring 2003, roughly 1 year before I bought the car at a dealership, from a turned in lease.

The mechanic told me the stop-leak was inserted improperly, and could have caused all the kinds of major problems. The dealership has since removed the upper intake and worked their way to the head, where they believe the problem is a blown gasket, although they are checking the heads. After the tests and repairs, if this stops here, the price is $2400. Gm has told me they will only assist me if its a workmanship issue.

My thought is that they screwed up the initial recall, or as they claim someone else wouldn't have had to repeat it, and since this build-up in pressure is probably what blew the gasket they should consider it a a quality issue.

Thanks for reading, and any info. comments, idea, or help is greatly appreciated.