Gotta love the 5.7 that Chevy came out with. I finished doing that to my 99 Denali a couple months ago, the PO had mixed the orange and green coolant and basically turned the coolant into an acidic sludge. I had to get the intake manifold hot tanked and surfaced, then had a flush a huge amount of water through the block to get all the crap out. It was a major PIA to do, but saved my a boat load of cash!
Did you need to get the manifold surfaced, or were you lucky enough to just blow the gasket?
ETA - I spent the day in the garage replacing the wheel bearings, rotors, pads, brake bleeding, oil change, and general checkup on my 98 S-10. Tomorrow I plan on cleaning the garage out and maybe washing the cars.