PeachParts Mercedes-Benz Forum - To buy or not to buy

I have never owned a Mercedes before, owned a couple of Audis and was impressed with them.
So the other day I'm coming around a corner and there is a 1970 280SE, 4 door. I see the price posted in the window and decide to stop and look. The body looks pretty darn good. Little bits of rust here and there, the largest about the size of a half dollar on the hood and overall just a real straight body, and all windows present and accounted for. The interior was really very nice, just a few holes in the leather on the back seat. Get this, someone along the way actually installed (poorly, I might add) a Radio Shack Realistic AM/FM Cassette. Yikes.

Anyway I finally got the owner on the phone and will get to take a look at it on Sunday. He told me a few things about it. He said that he didn't have time for it anymore and the big thing wrong with it now was that, when he starts it, it runs fine. But when he puts it into gear (Automatic) the engine starts reving and gets up to some pretty serious RPM.

I am pretty good mechanically. I've got all my credit cards paid off. The price is what i consider a fair deal, AND I've actually already gotten a little attached to it even though I have only seen from the outside.

So I ask, does this problem sound familiar to anyone and should I run, not walk, away from this little jewel. I know it may be as simple as some linkage that may just need a can or two of Gunk, or does it sound much more serious. The way this guy talked he hasn't tried starting or moving it in a while but says it runs and drives good.

Thanks in advance for any and all insight you might give.