Steve,

Use the search functoin on this page to find out some information about the OVP relay. Plenty of stuff out there-its a very common point of failure, and does give symptoms like you describe. The speed sensor went on my 190 and gave ABS problems like you describe.

The jerking on Drive is most likely flex disks (you have two of them i think) or possibly the rear subframe bushings (two before the rear axel, two behind it).

IIRC, No diagnostic sensor on the car that can hold codes, though you can pull codes while the engine is running. Pull plugs and see whats up, do a leakdown to make sure valves arn't burnt...just the usual brand of troubleshooting.

You sound handy-tell the guy how much it'll cost to 'put it right' and make him an offer if you fancy the car. You can get the 'official' manuals on CD from benz for 20 bucks, or check out websites like braingears that host 'em for free. Lots of good info and people on the board too. If you buy parts, buy 'em from phill on this website-it helps support the board, parts and cheap, and phill is a darn good.

cheers,
dan r.