Remote desktop works surprisingly well on low bandwidth connections. Videos and images can be a stretch, but it does degrade pretty gracefully. It's less secure than a VPN, but it's also easier to set up. 1k sounds about right for five terminal services licenses, which is probably the Right Way to do things if you're not going with a VPN. MSFT charges about the same for an XP license as a terminal services CAL, and terminal services will probably scale better. You could get into VMWare and virtual desktops, but microsoft still wants their pound of flesh.

It sounds like the previous tech guy just set up dynamic dns using his DNS provider. Just set up an account with dyndns or other dynamic DNS provider and set the router to update it.