Linda,
Take your time to find a good one. If you have to pay a bit more it will pay off in the long run. The concensious here seems to lean to the 240D with a manual transmission. Early 80's. Slow but steady; steady gets it!
Pull the floor mats and look for signs of water leakage, check the trunk also. Check the shocks for leakage. Every thing should work, though the cruise control commonly doesn't. Check my other posts about water leakage and fixes ( use the search ).
Finding and driving the right one will be a great pleasure and experience.

Good Luck
The Bern

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1982 240D 313,000 (4 speed)
1984 300CD 172,483
1985 German Shepherd Dog -Lacey- R.I.P.11/04/05

Hood Stars, Wrist Crowns and Obsession Dobs