Regarding repairs of wormy wood, or spalted rotten wood, 'Jasco
Refinishing products' makes a product called Jasco Wood Hardener, which
is available at paint stores, and Home Depot (big box stores).  It is
very free flowing and penetrates well in soft and open grain woods.  The
holes can be filled by injecting polyurethane glue into open worm
holes.  This glue foams up and expands to fill the voids.  It is a good
idea to apply some furniture around the area because the foam  will come
back out and could stick to the finish.

Bob Lemon
Lemon's Player Piano Service
Sacramento CA