This was shared in the SNS NG recently:
The 2 points I would make when undertaking this setup is:
1. Add the new server to the domain using the ConnectComputer function – NOT – during the install
2. Remember to install the Admin Tools from the LCS CD on the SBS box!! If you do not do this final step, the LCS tab will not show up under a User’s properties, and they will not be able to use any LCS service.
Other than that, it was actually simpler than expected. And, as a bonus, the CompanyWeb “Members” Shared Web Part now shows if a Member is logged in to LCS/Windows Messenger – without any intervention by me to set this up. Very cool!