Just wondering if anyone has had their lifters replaced and ,if so, how much did it cost?

This morning on startup the lifter noise was pretty pronounced; it was 48 degrees in the Atlanta area this a.m. I know as the temperature drops, its going to be getting louder and louder. After about five minutes as the engine warms the noise goes away altogether.

I've already run engine flush through with an oil change, so I think its probably wear and not just a blockage.

Lastly is this a possible DIY job and are there any special tools required ?