Thanks to everyone for your thoughtful comments and suggestions.
Yes, my Summarex was easily worth between $3000 and $4000, if the fungus could have been successfully removed.
This Summarex is the first version, complete with original caps and shade, and is the lens pictured in one of Jim Lager's Illustrated Leica Lens Guides.
I had no idea that attempting to remove the fungus was so dangerous.
The worst outcome that I anticipated was the failure to remove the fungus due to the internal glass having been permanently etched.
I could have lived with the etching because the lens was still useable.
But, my repairman did not disclose the possibility of total lens destruction, prior to accepting this job.
Maybe I would have taken the risk anyway....I don't know.
In the end, the 40-year relationship with my repairman is worth more to me than this monetary loss.
I've learned an expensive lesson with respect to future repairs of rare vintage lenses.