OVP may be the culprit but....
It's not that bad a job - really about 15 min swap on a C220. You say it bogged then quit running, and then refused to start.
Well there are two things that will (generally) cause a car not to start.
#1 lack of fuel
#2 Lack of spark
Granted there are a few other things, but most everything else leads to some sort of intermittent no start, or rough running condtion, not an absolute refusal to start.
What I would look at first, and what comes to mind is as follows:
#1 check the fuel pressure - is the car getting gas to the injectors? Im thinking a fuel pump failure may be your problem.
#2 Does the car have a decent spark? The other thing that comes to mind here is a bad coil or coil pack, causing the car to not produce a spark.
The fuel delivery failure seems more likely by the way you describe the slowing down and then stalling out.
A wiring harness wouldnt randomly "go" on you without exibiting symptoms beforehand. The C220 isnt generally plagued by the wiring harness problems that the C280's have been known to exibit.
It could be something as simple as a fuel pump relay.
I would definitely look at these issues before I spent any money on a wiring harness.
Hope this helps,
1990 500sl R129 - 76k Original Miles - New project - Follow the saga http://90r129.blogspot.com/
1990 190E 2.6 148k mi (sold)
1989 420 SEL 246k mi (sold)
1995 C220 175k mi (sold)
1992 190e 2.6 74k original miles (sold)
2000 c230 Kompressor 122k miles (RIP)
1996 C220 149k mi (sold)
2000 C230 Kompressor Sport 127k (sold)
2009 Mercedes c300 4matic
2006 Mercedes s430
2005 Jaguar XJR
2003 Cadillac Escalade