Tank you very much: advice please

Find a new restorer.
This guy is making work without good reason and wants to buy parts on your dime. Two strikes in my book.
Save the money and time for the things that will actually need fixing.

Heck these days one can 'look' inside a tank with scope.
Be real careful removing the fuel sender. Check the brass contact that runs on the resistance wire is intact. Change the sock filter if it needs. If its cruddy maytbe the tank should be cleaned as others have said. If it the filter is clean, then take a look inside if you're still concerned.