your pricing for the A/C reciver is off the charts, its between 20 and 35 dollars depending on what brand you get, the genuine MB part is close to your price though, but then your compressor price is not the genuine MB part range, its aftermarket range.

The chinese origin sanden type compressor works a treat. It looks physically different but works perfectly fine.

the tranny is not to worry about if it was actually rebuilt, but you need to find out what rebuilt means, was it new wear parts and seals or just an ATF and connector plug change.

the engine smelling rich on startup is quite normal, the ECU is doing that to ignite the cat converters. Weak in the front end could be bad shocks or bad ball joints etc. (ball joints wear out fast on the W210 and are quite easy to change out)

rear window regulator is a normal break item on a W210 - if you are in the southeast, better just prop it up inside the door and leave it be for the time being. Sagging headliner is also very common, you can buy new OE type material or go a bit fancy like alcantara which will look more elegant IMO.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)