School file / print / management server ideas

So... I am trying to help a (very) small school actually get some IT going. Could I get some opinions on how to build a low-cost file and print server for a place with about 50 computers?

Right now, they're running a mix of MacOS X and Windows XP Home / Win98. They have NO server to speak of (not even an IT guy), and teachers print by connecting to some other workstation's shared printer or they figure it out on their own. They have no backups whatsoever, and many computers don't print because they don't have the right drivers installed, etc. I think they should have some solution that costs very little in recurring maintenance, and I'm torn between the options at this point.

I was thinking of 3 ways to go about this, but I'd love to see what others may recommend...

1) Buy Windows 2000 Server (because it's cheaper) and get 50 CALs.
Perceived pros:
- Any IT guy should know how to help them administer a windows server.
- File sharing and print services are built into the OS, no additional tweaking required.
- Domain controller could help them manage group policy, push software updates out, etc.
- Other software (antivirus management, etc.) can run straight on the DC.

Perceived cons:
- I still think that'll run over $500 for the software licenses, right? Then upgrades, of course.
- System maintenance will be essential if the server's to be kept virus-free. Will maintenance cost more?

2) Build a Linux server that has Samba / CUPS services
Perceived pros:
- Very cheap (free) to set up
- Many features can be added to the server
- Not very susceptible to viruses or other security holes (provided auto updates are in place)

Perceived cons:
- Unfamiliar interface for the non-technical administrator
- Services will have to be set up manually, perhaps tweaks will have to be made to be compatible with newer OSes.
- Can 3rd party software run on this? (i.e. antivirus managment)
- Not any IT guy will know how to fix the server?

3) Buy an appliance built for the job, like the PowerElf II (http://greencomputer.com/solutions/school.shtml)
Perceived pros:
- Quickest setup (possibly)
- Many services provided out of the box (including ones they probably will never need, like email hosting)
- Automated maintenance and backup is part of the system.

Perceived cons:
- Initial cost is $2000 at least, possibly more for hardware maintenance
- Vendor lock-in is possible
- Incompatibilities with 3rd party software??

Anyway, I wondered what you all thought.