I have a 1999 C230 Komp with 69K-- For the past 6 months my Check Engine Light has been going on/off periodically. I brought my car to AutoZone for a diagnostic Check, and was told that the code was 1070 or Fuel trim-Bank 1 was faulty. I need some help on diagnosing the problem- the guy in AutoZone told me it was a Bad Oxygen Sensor. He said it was the one on the exhaust manifold. I am confused on buying eith the OEM O2 sensor or the Bosch Universal? Also how hard is it to replace?- Seems like my hands could not fit reaching down from the engine compartment?- IS there a special tool?- Any help would be appreciated- I am trying to sell this car - I have a 2002 E320 in my driveway waitng to replace my 99 C230!

 

First off, I have a different engine configuration than you. On the V6, the upstream sensors (nr. the exhuast man.) are indeed more difficult to get at. The downstream sensors on the '99 V6 are user friendly and take less than half an hour to change. Most of that time is spent raising the car high enough to get under it.
I found the price of a Bosch replacement sensor can vary by as much as 50%. I purchased mine online at All Oem Parts and with a Bosch rebate it cost $94.
Good luck.