LDAP auth on SME is still a work in progress, so I wouldn't go there yet.
However, winbindd auth does work out-of-the box. The place to be looking for answers to this question is over on the Ubuntu forums. You'll want to look for help at setting up Ubuntu as a domain member with winbindd. My guess is that there's a ubuntu package in the mainstream apt repositories to set this up for you and provide a nice GUI app to configure the client.
You'll also want to look over on the Ubuntu boards about what it takes to setup profile mapping. If SME can't do what you need, then come back here and state specifically what Ubuntu needs from the server to provide profile mapping.
Greg