Yeah this is one of those times for being on a domain is helpful. All computers would be authenticated against the server and which service likely wouldn't matter. But, a small reason to go with a domain.
The backup program can be on any computer as it uses the .xml file to know where the databases are. However, if you still have trouble, I would at least try using the backup program on the main computer.
As far as workgroup names, there are only a few limitations. They generally have to be less than 15 characters. They can't have spaces. They can't match any computer name but must match all of the other workgroup names. MSHOME and WORKGROUP are just default workgroups with MSHOME being newer. But, you could have Amazing or Snowman, doesn't matter. Just play around with it, you'll get it, just get off the local service.
