Yukon Denali engine ticking

The lifters can most assuredly be replaced. But the cost would exceed the value of the vehicle. On a 20 year old vehicle with nearly 100,000 miles on it I would recommend using a heavier weight oil and just keep driving it. If the vehicle sits a lot I would also recommend using it more often. More frequent oil changes would be helpful as well. Replacing the lifters is also a major job which will require most of the wiring to be disconnected and moved, accessories like the air conditioner compressor to be moved out of the way, etc. Keep in mind that most of these items have been untouched since the vehicle was new, 20 years old, and will surely not like to be moved around! I can guarantee that if you decide to replace the lifters the aftermath will be unending problems! Hope that helps! Jim