Unfortunately, Exchange uses the same NetBios ports that the rest of NT file/print sharing does. So, to open up full access to your Exchange would also open up total access to your file server. NOT a good thing.
If you really have to work from home, I'd suggest one of two things:
Install Outlook Web Access on your server and adjust your firewall to forward port 80 to the mail server. That way, you can send/receive e-mail via the web from home.
Setup IMAP/POP mail on your server (on by default) and forward tcp port 110 (for POP) or tcp+udp port 143 (for IMAP). POP lets you pull your messages from the server and work with them. (But remember to configure your mail client NOT to delete the messages as it pulls them!) IMAP lets you work on your e-mail at home using folders stored on the server. Unfortunately, Outlook 2000 only supports POP, so you'd have to use something like Outlook Express for IMAP. Pretty good mail client, IMHO.
So, there's really not a good way. If your firewall is flexible enough, you could try to permit access to your network ONLY from your home IP address, if you have a static.
Best bet would be to get your boss to ante up the cash for a cheap VPN solution.. A couple of hundred bucks and you could be on your way.
- G