[There are a lot of sculpture instruction programs based in Pietrasanta, the marble quarry area of Italy. These are mostly based on the premise that people are willing to pay for this instruction, however. Check Walter Arnold's site for a link to one of these; it's on my Custom Art Referral list.
Finding a master sculptor willing to take on an apprentice might be difficult without going to Italy, but you could look around the Web for sculptors whose work you admire, then contact them individually. Try some of the major art registries I've listed under Resources/The world of art online.]
UNITED ARTWORKS- Sculpture, Jewelry, and other art stuff
http://unitedartworks.com Useful Resources, Technical Tips, and Art in Various Media