Looking at a 1994 E320
 

I have my eye on an E320 that looks to be in good condition other than a transmission on it's way out. It has less than 150K on the clock and the price seems reasonable. I already have a daily driver, so I can take my time addressing the transmission issue. It won't go in reverse, but I'll be able to give it a healthy test drive.

How can I tell if the wiring harness is updated in case the owner doesn't know? Anything I should look for or listen for while driving? Thanks

No reverse problem is almost certainly worn out B3 clutch discs. Fix requires transmission to be removed and disassembled. If you don't DIY, figure a minimum of $2000 for a shop to do it.

J. M. van Swaay

What if I bring the transmission to them out of the car, then re-install it myself?
Do you have a guesstimate as to how much I'd pay for that? Thanks