Moving from Windows Server 2000 workgroup to Windows Server 2008 domain

Solution 1:

Yes the computer will be able to access the shared resources on the windows 2008 server- albeit every time the users will have to provide their credentials to access shared resources.

Ideally they should be joined to the domain, to enable centralization of users, management, group policies , and windows update via WSUS. Joining "should not break anything but keep in mind that users will have new profiles- so there might be some initial configuration. But having workstations and users in a domain is definitely worth it.

Solution 2:

Joining them to the domain won't break anything. For a small enterprise, you can go with SBS 2008 (or 2011 if you're feeling saucy) and have all your goodies in one basket. AD, Exchange, file server, etc.

For a basic setup, you can keep it simple and manageable. However, I would advise you to hire a consultant to periodically come in and perform maintenance, backups, disaster recovery, etc.