[ActiveDir] SBS 2003 new to domain

[Douglas W Stelley]

Hello all

        I have a small AD domain, 3 sites, 3 DC's, around 200 PC's (2000 & XP), Lotus Domino and Citrix.
We have a full trust relationship with a second AD.

I may need to introduce SBS 2003 premium as a new installation.

I realize SBS has to be at the root, and that's OK to me since it will upgrade this domain to a 2003 vs 2000 AD structure, but what of the other DC's and Lotus?

When I install this, will it join the existing Domain, and assume ownership roles, or will I have to create a new domain and migrate everything in?

I really don't want to have to do that, even in this small scenario, it'll get complicated in a hurry.

My other option, but perhaps a $costlier one would be to buy a 2003 Server and SQL 2k separately. (because of Domino, I don't need/(but would rather have) Exchange)

The vendor strongly recommends SBS2003, but I wonder if that is in our best interest?

I have no experience in SBS so I need y'alls expert advice on this one, thanks in advance
Doug