As the owner of an '85 190E, I think I can give you some insights. The dash cracking is common, infact finding a non-cracked dash is probably harder. The repairs for this cosmetic flaw rangers from the carpet toppers ($40), a fitted/molded plastic "dash cap" ($90) or finding an uncracked dash at a recycler ($100?).

The '85 does have the benefit of more HP over the '84 due to increased compression and a modified fuel injection system. As you said, the ABS and airbag were the few options available (Orthopedic seats, Leather and Metallic Paint were the others) for that year.

Service records would be of great help. The timing chain tensioner and rails should have been done. Start the car, and listen for chain rattle before the oil pressure build up. Check the cylinder compression and don't be surprised if the valve seals need to be changed, that's very common in the M102, and luckily fixes most oil consumption problems. The cooling system is pretty straight forward. Have the serpentine belt (cracks?) and the belt tensioner checked, that's a $100 part right there.

At this age, pretty much all of the rubber suspension bits should have been replaced, including the motor mounts, subframe mounts, ball joints, tie rods, driveshaft flex discs, and pretty much every other plastic/rubber joint in that famous multi-link suspension. Hopefully the shocks have been changed out.

The A/C system should be checked for leaks and the service record examined for problems. That's a pretty expensive little, and I emphasize little, system that MB put in there.

It's a great car, even now, just have to remember it's going to be showing some age in the joints.