John:
Keep your car. The older it gets, and the better maintained you keep it, simply conspire to make it more of a jewel. That's a nice ride you have there.
Now, I specifically picked a 300TE and a 500E myownself, 'cuz I seriously intend to keep them forever. I've been in a bunch of chassis, and really like the W124 (though I don't think the 500E is a W124; too nasty
) so my thought is to find a Benz you like and keep it forever...'cuz there's nuthin' safer (my patent excuse for owning a 300+HP sedan!!).
Enjoy your ride.
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Best regards, Michael
'92 500E
'88 300TE