Migrating Wordpress Site to Wordpress MultiSite

Is there any documentation on migrating an existing Wordpress 3.0 site to a WP MU site? I'm comfortable with migrating regular Wordpress sites to another server, but now that I've begun with MU I'm not so sure.

I've done an XML export of the content of the to-be-migrated site, and I've created a site for it inside the MU network (to which I'll import the XML once the file paths have been updated). But now I'm struggling to identify where on the MU ftp I would place the /wp-content/uploads folder?

I noticed that when creating a site on the MU this did not populate the blogs.dir, nor did a test image I uploaded show up there (or anywhere else that I looked).

Any insight would be appreciated.