$4500 sounds right for a GM engine. Even the old small blocks get up into the $4000 range when you factor in the water pump. belts, hoses, spark plugs, wires, oil, coolant, filters, etc... Also, that way, you have a warranty that's good with any GM dealer, instead of possibly a warranty for the work done on your existing engine that's only good at the dealer that did the job.

True though, a 5.3 is a tough little motor with very few problems to worry you. The worst I've had to do to one is replace a set of lifters in an '03 Suburban with just over 100k miles, which requires removing the heads. The lifters were very slow to pump up because of irregular and infrequent oil changes.