I doubt anyone would have the tools of equipment to enable such a task and ensure it would meet the required standard after the process.
I do remember (maybe 40 years ago) it was possible to replace the tube insert in the housing with a special kit supplied from the manufacturer.
These days returned tubes in their housings are stripped down to recover all materials and some parts are remanufactured for use in new products, if they pass strict criteria.
The equipment needed to manufacture, align, and certify a X-ray assembly is beyond anything that could be done in the field.
P.S. The same is true for digital imaging detectors.
