Looks pretty good.

The black engine known as the M103 I6 is a very reliable unit but also prone to oil leaks around  the gasket area. Oil,  plugs and coil make sure it's been changed, service records, the usual stuff.

Check make sure it doesn't leak. One unique thing about the 124 is that the carpet which comes with a sponge like material underneath can be removed on the driver and passenger side. Make sure those aren't wet as, some cars tend to rust near battery tray area (due to lead acid batteries) or the drains tend to get close to clogged by leaves, thus causing the water to enter the cabin and cause rust.

Interior build quality is really solid for a 25 year old car. But do check if the electronics are working, lights, air con, tyre wear, exhaust leaks, cold and warm startups.

Good luck hunting for the last great Benz!

Don't change it to 2JZ la, still maintain using Merc engine but change to the 3.0ltr 24v and keep it as original as possible.

true, i hate those idiot everyday asking change 1jz, 2jz, rb, sr and bla bla ........ if wanna change, change same manufacturer .....
me still looking K8 engine from mazda for my miata

Well I won't go so far as calling them idiot la! For cars that have not much classic/collector value, then probably still ok but for this W124, I feel should try retain the classical feel and originality of it hence retain using the same brand engine is the best.