Any update on this? Still ticking?

I have a ticking C320 with the M112 engine. I replaced the lifters on the passenger side a while ago, which did not fix the noise. However, I noticed that the lifters fit tightly in the rocker arm bores, especially one arm that may have been too tight. My theory is the lifter is stuck in the arm, and the spring is not enough force to expand it. I need to remove the valve cover again, pull one spark plug from each cylinder, rotate the crankshaft by hand, and check for excess tappet clearance. My guess is the tight lifter is not working at all and will have a large gap between it and the valve stem. Hopefully this has not damaged the cam lobe or top of the valve.

If this is the case, how difficult is it to replace one rocker arm? I understand they are pressed onto the rocker shaft.