Setting Up a VPN on W2K

I have a Windows 2000 Server (PDC of my domain) with Active Directory activated. I also have a LinkSys BEFSR11 Router/FireWall.
I’m connect to the Internet throught cable modem.

I want to setup a VPN so my users (about 10) can access my server via VPN. What I have to do to setup a successful VPN ? The users use Win98/Win98SE.