At around this mileage and with age the fuel pump relay becomes erratic leading to engine shutoff's ,though the car restarts .A new relay is best ,but can be re-soldered .Same replacement holds good for the over voltage relay.

Fuses ; almost all the fuses become age eroded and lead to intermittent electrical faults including occasional flickering gauges and lights .Best replace all fuses from a fuse kit with brass fuses clean the tangs.Visual check fail to detect the bad fuses ,but does under a magnifying glass.

Idle control valve needs a good clean and rubber vacuum pipes replaced if hard.

ATF leakage is almost certainly due to a leaky vacuum modulator a low cost replacement.Shift quality will improve in smoothness.

Alternator replace the regulator or the unit itself if the commutator has a wear grove.The belt tensioner will likely go bad if you remove the alternator so its best to replace the alternator,belt ,tensioner in one go.
This will make the car reliable for a long time .I think of them as 20+ years consumables.

I hope this assists in your serviceing based on my experience with this very reliable model.
mak
300se W126