Repair or Rebuilt

90% chance the oil consumption is also head gasket related.

replace head gaskets, water pump, thermostat, all belts and hoses as well as all engine sensors (before they go bad)

probably looking at $1500-$2000 for labor at a shop to do the work if they charge you fairly.

once they pull the heads they can tell you if the cylinders are worn suggesting more is wrong other then just the head gaskets

This was a known problem and is very common on the V-8 back then. My son has an 04 with a 4.8L. We got the truck with 134,000 miles with lots of problems including heads leaking coolant and oil for free. Our leak was very slight, but you would need to add oil and coolant every three weeks are so. Spoke with a few guys on silverado websites and they had great luck with a product called liquid glass for head gasket repair. It runs from $8.00 to $60.00 a bottle. We bought 2 of the eight dollar bottles and followed the instructions to the letter. No more leaks and the truck now has 155,000 miles.