Blown head gasket

Have a 2001 chevy s-10 4 cylinder with 85,000 miles. Had a blown head gasket due to overheating, spent $2,500 getting it repaired, cleaned heads etc. When got back first day on the road, began clanging very loudly like a valve noise, mechanic says "lots of sludge in engine and only option is to rebuild or replace engine for $3500-$4700". My question is this, would you not have pulled the pan and/or checked the oil pump before reassembly, or done an engine flush. Grew up with a father in a garage and the car belongs to a friend and I do not believe they followed good shop practice in diagnosing and repair advice, what protocol would you have followed with a blown head gasket.

Thanks