First off a car with 68,000 miles is not high. It should not make excessive valvetrain noise. I wish these cars had the quiet, more powerful, bulletproof, and way more inexpensive to maintain Chrysler 3.5 V6. A LOT of these cars have lifter noise.

My car went through a spell between 12-18,000 miles where it sounded like it had a collapsed lifter when it was cold. I changed the oil and that didn't help. One day I just got tired of it and flogged the **** out of it a few times and it went away for a while. The noise came back a couple hundred miles later and I flogged it again and it went away and hasn't been back and I have 31,000 on it now. It still has a faint tick but that's normal for the most part for these Mercedes engines. My car has had a bit of a rough idle and valvetrain noise since I got it at 5,000 miles.