weird engine noise

i have a 1990 buick lesabre with 130k miles on it. When i start it up and it runs at idle speed, i hear a really strange noise coming from the engine that is is hard to describe. Its a "chattering" noise and sounds sort of like a bad bearing. I check the water pump, alternator and p/s pump and they are fine. I listened more closely and it sounds like it is coming from the cylinder head. I'm not sure if its the camshaft, the rocker arms, pushrods or what. If anyone could help, id really appreciate it.

Could be a shot lifter, but the only way to really get at the heart of the issue is with a trip to the mechanic.

Yeah, I agree, what you are hearing is the lifters. Off to the mechanic.

How hard do you think it would be to change the lifters? I want to do it myself so i dont have to waste a shitload of money to have a mechanic do it.