Can Site/theme Cloning Be Done, And If So, How?

I have a bunch of sites in a multi-site WordPress installation. Site B has a highly customized theme (including a number of specialized options stored away in the options table). Site B also has a ton (a TON) of post data, something on the order of 12,000+ posts.

I would like to create a new site, Site G. I'd like Site G to look identical to Site B, but with all new posts. Is there a way to extract Site B (including all the customizations and options), import it as Site G, and then, presumably, kill all the posts, tags, and categories, and start the content part of the system over?

If this is doable, any tips on how?