If you can get an engine PCM from a same year/model as your Avalance you will save using up your licenses on HPTuners. You can get a PCM and have it loaded with the base Av program and then tune it with your standard cable. I'd sure do the 6.0L engine but it's not going to be a straight swap. For simplicity and speed to get back up and going, it's hard to beat the 5.7L Vortec replacement engine. If you have the time to allow the vehicle to be down, the 6.0L is great. You can bolt the 6.0 to the suburban trans using a crankshaft spacer/extender. You'll need engine adapter plates, a wiring harness, fuel system connections, fly by wire throttle pedal and sending unit (if FBW not cable), radiator hoses, air intake system and a few other items. If your wife is anything like normal women, replace the 5.7L and be done with it, not worth the aggrevation.