System 6 can connect to a System 7 - 9 Mac with File Sharing and access files without any trouble at all, I've done it myself. However a System 6 Mac can't share files without the use of third party software.

As for the LaserJet, does it support classic AppleTalk, or just AppleTalk over IP? If it only supports AppleTalk over IP you are SOL, if it supports "real" AppleTalk, however, you should be in luck so long as the LaserWriter software for System 6 supports it.