I bought a banged up 1996 C280 with suspension issues and no A/C in 2003 for $3K. It had 222,000 miles on it. It's still in the family with over 280,000 on it. It has always been a daily driver.

Last summer I was trying to buy (locally) a banged up 1996 C280 with 25,000 miles on it. I could have gotten it for under $6K. I took it to a Mercedes dealer for a PPI and learned that nothing had ever been done to it - even had the original fuel filter. It needed everything that every 96 C280 needs:

new head gasket (which i knew)
shifter bushing
lower control arm bushings (even with 0 miles, they are shot on this car)
and maybe some other things that i've forgotten.

I passed on it, because it needed a couple grand in collision repair work. The guy sold it on Ebay for close to $7K, I think.

I do not believe that you have to worry about the wiring harness on a 96.

Don't get me wrong, in addition to the items listed above the original owner and I replaced zillions of things on the 96 that I do own. Typical items are:

windshield wiper motor and transmission
combination switch
water pump
duovalve
transmission mount (and tear out insulation above driveshaft)
power steering pump
lower ball joints
sway bar bushings
Oxygen sensor
EGR valve
mass air sensor
A/C condenser
fresh air vacuum element
exhaust gasket
radio LCD display
visor mirrors
sunroof headliner

plus many others.

But over 15 years and a quarter million miles, you are going to be replacing things. It is to this day a nice driving (though now rusting) car. It's a way better car than our 2001 S430 and 1997 E420. Period.

I won't pass judgement on the asking price, but I would want to know what's been done to the car so far before making an offer.