This info is from MB USA website:
For the 1991 300CE:
1,929 units sold in US
MSRP $57,350
3.0 litre 6 cylinder 24 valve engine
217 hp @ 6400 rpm
195 lb ft torque @ 4600 rpm
Fuel & Ignition system KE-5
Compression ratio 10.0:1
PREMIUM UNLEADED GASOLINE

My advice is to get the VIN & immediately do a carfax on it. You will know how many times it's changed hands.
Then inspect the service records. Is the "mechanic" the seller (or a former owner)?
Were the valve guides replaced when they pulled the head? Valve guide wear was a problem on some years of the 3.0 engine. I don't know if yours would be in that category. MB switched to the 24 valve from the older 12 valve 3.0 in 1990, so you are the 2nd year in that 3 year engine run. In 1993, they went to a 3.2 litre 24v mill.
Sounds like the description you give is from an ad. Check it out well.
If you are in New England, look closely for rust. The more owners, the more likely one of them skimped on maintenance.

The oft repeated saying here:

There's nothing more expensive than a cheap Mercedes.

But, I own an 88 300ce and love it.
And I'll bet your wife won't like you driving "her" car all the time.

Good Luck.