My 1993 30D feels likw it wobles at little at slow speeds, and on the highway at 65mph or more the steering wheel vibrates. any ideas on what it may be?

First rotate the tires. If there is no change, check the steering damper. If that is fine, you could have a bad hard part in the steering. You could also be feeling driveline vibration.

I've got a '80 300sd and the same exact thing happend. the steering thing at low speeds for me was fixed for ~$75 by a mechanic messing with something in the steering column. the vibration is due to the tires needing to be balanced, no tire is exactly round so they need little weights on them. most tire stores will do this for about $5 a tire. hope this helps.