If you're aiming to rehabilitate it, I suggest moving it outside into a semi-natural enclosure. Keep feeding it at the box, but let it pretty much explore on its own. Woodchucks typically disperse near the end of their first summer and yellow-bellied marmots typically disperse during their second summer. Females probably make better pets than males, but I've heard some good stories of males kept as pets. And, it can go into torpor any month.
Marmots are rodents so make sure they've got something to gnaw on to keep their teeth worn down.
Some people have written in to say that their pet marmots have toilet trained themselves. In nature, some species often defecate just outside their burrow and then use the feces to make a plug when they hibernate. Write me with your successes and failures and I'll periodically update this brief guide.