Cost of replacing oil feed tubes?

What is your question?

Engine ticking sound, from the driver's side slightly towards the front. Ticking is faster when depressing the accelerator, not sure if it goes away or I can't hear it if rpm more than 3K or highway speeds. No loss of power. Does not seem to have low oil pressure but a slight and gradual oil leak towards the front of the engine. 105K miles.

How long has your 1999 Mercedes-Benz S420 had this problem?

About a year, but the car was garaged and not being used.