Johnp,
Lifters are not hat hard to replace yourself. You can replace all 12 @ around $15 a piece in a few hours. The most cridical part is correct torque specs on the rocker towers and tightining them evenly. You can opt to replace just the ones that are ticking. You can check them by feeling the spring tension sticking. Also, you can run the engine at idle with the valve cover off for further diagnosis,,,, So i have heard.
Good Luck!
Adam

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Current Stable:
01 ML55 AMG
92 500E (a few mods)
87 300E (lots of mods)
00 Chevy 3500HD Diesel Box Truck
68 18' Donzi Marine
06 GT i-Drive7 1.0 Mountain Bike (with GPS!)

PREVIOUSLY OWNED:83 300SD, 87 420SEL, 88 420SEL, 90 420SEL, 86 560SEL, 86 190E 2.3-16V AMG, 94 E320