Repairing it right away is good advice.

This really isn't that bad from what I can see. Fairly straight forward repair.
$5k is insane. They clearly just don't want the job unless they can gouge you on it. Should be hundreds, not thousands.
A dealer is not going to be a good value for this type of work either.

You might try a welding shop. I have found that they tend to be far cheaper for structural work like this. This is not a matter of great precision, and no bonus points for aesthetics under there!
Body shops (in general) do insured work, so they tend to not compete on price.
A good welder will fix that forever. Stronger than new!

This is not the end.
Best of luck.

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1986 300E 5-Speed 240k mi.