How to unify Unix386, MAC, DOS/Windows under one network?

[Harry A Levinson]

I would like to use a Unix 386 box running Interactive Unix as a file
and print server for one or two macs.  There are already a couple
of DOS machines using PC-Interface on this system.

1.  Is there a TOPS like product for non-Sun unix?
2.  How about any other appletalk server software using either ethernet
    or an appletalk network board for the server?
3.  We have NFS though it is not yet installed.  Will this do what I want?
    Is this my best shot at bringing Unix/DOS/MAC all under one network?
4.  Do any of these allow unix mail to be routed between the macs and 
    DOS/Windows?
5.  Is there a program similar to PC-Interface which would allow the
    macs to be connected over a 19.2k or 38.4k baud RS232 serial line?

Sorry for the rather broad questions (especially if they have been asked
already) but I have not been able to find a dealer who can address issues
regarding all three operating systems and architectures.

Many thanks in advance.  Respond via email and I will post a summary.
harry
hal at world.std.com