When the 500E arrived over a month ago, I was pretty happy with what I saw. There were no major surprises, and the seller likely even "over-sold" the cosmetic faults that the car has. The only real area of concern that didn't come through in my discussions with the previous owner was the health of the transmission, which was weighing on my mind as an area of possible concern. The W124s are not immune from needing transmission replacements, so I hoped that wasn't in my future.
With the car at my local shop, it all seems like mostly good news. The biggest issue outside of the transmission bushings (which are non-existent) is apparently a transmission mount that is in very, very poor condition, and likely a major player in concerns over hard shifting and some reluctance to engage reverse. Combining the bad bushings with a bad mount will almost certainly create the conditions I'm seeing, so here's hoping that with those fixes made, the transmission feels healthy once again.
Other issues seem fairly minor, aside from a leaking rear shock. The rear SLS shocks are NLA, which means you have to live with bad shocks or pay some scalper $1000 for one shock (yes, really). My only hope is that the leaking is attributed to the rear accumulator ball, and/or that the one used shock I managed to track down will work in a pinch.
There are some minor fluid leaks and bushings that need attention, but overall, for what will absolutely be the cheapest 500E to sell anytime now or into the future, it's mostly good news.