The oil creeping up the wires & damaging O 2 sensors, Engine Control modules, etc. is a VERY common problem on your particular engine.
It is caused by a leaking camshaft adjuster solenoid on the engine.
When a harness is replaced, ( along with a new camshaft adjuster ), there is a special adapter cable that has to be installed at the same time, to prevent the problem from happening again.
This is the part that MUST be used:
http://www.jomb.de/1.jpg
And this is where it's located:
http://www.jomb.de/neu.jpg
If they did not replace the oxygen sensor, that could well be your problem.