I JUST did this on my daily's 5.3 (2005 LM7, same thing). I've done them in the past but I bought a book about rebuilding an LS because a simple regasket and cam job turned into a full ring and bearing. The book wants you to do the rear main plate first, then the front cover, then the oil pan.
A few notes that I have not done in the past and I think that's where my oil leak struggles on my C10's 5.3 have come from:
Go ahead and change the barbell while you're there, it's o-ring is likely flat
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Put the rear main plate on with the bolts barely hand tight, I actually backed them off a bit from hand tight. Then spin the crank a couple rotations to help it find it's natural center
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Then take a nice quality straight edge and check the alignment of the rear plate vs the oil pan rails. The book specs the rear plate be no more than .020" lower than the oil pan rails. Then torque the rear cover bolts down to spec, 18ft lbs.
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Then do the same thing with the front cover. Put it on with the bolts still loose, put the balancer on to help center it and turn the crank a couple rotations to help it find natural center. Then check it's alignment to the oil pan rails with the straight edge. Same spec here, no lower than .020" below the oil pan rails. The torque the front cover bolts down to 18ft lbs as well.
Then put the pan gasket on and drop the pan on. The book calls for a healthy glob of RTV in the corners where the front and rear covers meet, I put a light coating of RTV all the way around on both surfaces. You decide how you wanna do it. Then put the bolts in to get the pan roughly located, don't tighten them down yet
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