Chevrolet Repair: 99 gmc seirra 4.8L lifter, gmc seirra, timing chain cover

Question
i have a 99 gmc seirra with a 4.8l engine it has about 100,000 miles on it. i took it in for an oil change a couple months ago and the person there suggested that i get the engine oil flushed. at the time i thought it was a good idea so i had them do it. since doing the engine flush my motor has developed a "random" lifter tick. by random i mean it only happened after sitting sometimes.  it would tick for a little while then i assume that the lifter built pressure and it would get quiet.in the last couple of days it seems to be getting more regular and lasts longer do i have a bad lifter? how difficult is it to change? how far would i have to tear down the engine to be able to remove it? can i change only one or do i have to replace the cam and pushrods too?

Answer
If it were my truck and I seriously wanted to keep it a while, To fix the lifter would require: Taking the intake off, removing the valve cover on the bad side, and inspecting the bottom of the lifter to see if the cam has been damaged or worn. If the cam is damaged, then you will have to remove the radiator,condensor, and just about every accesory you have on the front of the motor. Then the timing chain cover and the timing chain. Removing the cam will require removal of all lifters and pushrods and rocker arms.
It does sound like you have developed a weak lifter from your description.