Do you have pictures of the car?
Once the problems are sorted, you may find, if the car has not succumbed to rust nor rot, you have a safe, comfortable car that could last you for hundreds of thousands of kms. 139,000 is NOTHING for a well kept 6 cylinder one of these cars.
I have always been bewildered why, in your country, these fine cars have never received their proper attention and adulation. "Crapheap" indeed? A Renault Clio is more worthy of that moniker. In your country my observation is that cars are discarded like used tissue paper every 2-3 years. Because of the MOT tests, or for whatever other reasons, vanity, the strange "company cars" phenomenon, or whatever....
A W126 Merc is the opposite of all that, it is engiineered to last decades.
YOu may find you want to keep it. Also, have a look at
www.benzworld.com in the W126 section, which has been acclaimed to have the most intense worldwide focus on these models. I am a moderator there and would welcome you. But if you sign up, don't do so as Crapchallenge, your welcome could be chilly.
Good luck in your endeavors.
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1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ...
1995 E 420, 170k "The Red Plum" (sold)
2015 BMW 535i xdrive awd
Stage 1 DINAN, 6k, <----364 hp
1967 Mercury Cougar, 49k
2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive

(sold)