dbunke

You said you changed the oil a couple days ago, did you see or look for glitter in it? A chewed up cam and lifter usually leaves something in the oil. No glitter, I would open it up. 15 hrs seems high just for tear down..... 175K, there is plenty of life left in it.

On the LS motors lifter replacement does involve removing the Cylinder heads so it is a bigger job than most engines. No hard to do just more involved and costly at any shop.