Well, I haven't performed that operation just yet but I'm sure I will have to at some point in the because my avalanche has a lifter tick and about 2 months ago, I'm cruising up the interstate, two hour drive to catch a 5:30 am flight. Suddenly I heard what sounds like the blower motor rattling. Turns out it engine noise. I pull over about an hour from the airport and inspect things while my wife runs in the store to grab some breakfast. My plan was to drive it on until it quit (I figured it was gfailed lifter but it did sound almost exactly like a rod knock, on the rear section of the passenger side). Fortunately after about 5 min at idle, the noise went away. I limped it to the parking lot at the airport, never getting above 70 mph. Our return flight didn't land until 1:15 am on a Saturday morning so I was hoping it would get us back home.
After doing something thinking on my week long vacation, I decided that the o-ring on the oil pump must be bad for sure and the reason for the noise was a starved lifter. After letting it idle, it got the proper oil flow back and lifter noise went away. That being said, the way to test the o-ring is to pour 2 additional quarts of oil (if its full on the dipstick). That gets the oil level above the o-ring. I stopped on my way home and did that and ran 80-85 mph the whole way home without any noise. I've since driven it over 1k miles like that and haven't experience that sound again, just the same lifter tick I've had for the last couple years (and smacking at start up). My thinking is I'll just run it with 8 quarts of oil until something fails and I'll fix it then. For those who say to knot run it with extra oil, we ran our work truck like that over 200k miles (with the two additional quarts of oil because the o-ring was bad).
As far as replacements, I think you just pull the intake and heads off, replace the lifters and reassemble. Probably a bastard of a job but doable. I'm crossing my fingers that I don't have to find out for a long time.
