Welcome to the group!

No need for a leakdown test if the compression is OK, but you can tell that, pretty much, by starting it cold. If it starts right up when the glow plug light goes out and doesn't make more than a little puff of white smoke, the compression is fine. If it starts hard, by all means get compression checked, and if low or variable between cylinders, do a leakdown check.

Engine and transmission mounts will be shot by this time.

Also check the brakes -- for some reason, owners of older MBs that don't want to keep the car feel compelled to cheat on rotors, and end up damaging the cailipers from running the rotors too thin (I've seen this on about six car so far, no exceptions......). Not a big deal, but a cost to deduct from the purchase price.

Check front suspension -- lower ball joints are hard to remove and replace. Track rod bearings ditto -- track rod to body bushings are easy.

Examine underbody for rust -- this can get expensive. Check the drains at the front fenders (under vent grille and at battery) for clogs and rust. Check trunk drains.

Transmission.

Things you can pretty much expect: Engine and transmission mounts, and engine shocks. Unless previously replaced, these are all shot.

Probably needs rear subframe bushings and differential mounts, too. Window seals front and rear are probably shot, need to be replaced to eliminate/prevent water leaks -- the water will rust the car out.

Door locks and ACC vac systems may be flaky -- this is almost always a vac leak, may be servos. Variable difficulty -- ACC servos are a pain.

Driver's seat springs are probably soft -- can be replaced easily, but not particularly cheap. Note that the driver's seat has a hieght adjustment, low seat may not be bad springs.

Good luck!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!