Um, I was assuming that you have used remote desktop or terminal services before. But, I was wondering, have you? If so, then this is a really straightforward process for you. If you need any help, just ask.
I am not sure about the remote assistance, but If you connect to a Windows 2000/.net terminal server with anyother client than windows 2k/xp you'll only have 90 days to use it. That is unless you fork over the money to buy clients. Windows 2k/xp come with a client and 9X do not.
You only get 2 concurrent connections in administration mode, and you can connect with pretty much any MS OS (and even Linux with a special utility). As for NT Terminal Server, I am not aware of any special licensing other than general user connections (CALs) to it to begin with, so the OS *shouldn't* make any difference.
Back to WinXP, here's a link from MS giving a pretty good overview about it:
This link begins to show how to enable it and how to select non-admin users to connect to it.
Once you start using it, it's hard to go back. I administer 7 servers with TS, and another 10 WinXP workstations/laptops (test rollout on these babies) using TS/Remote Desktop/RDP and it makes life MUCH easier.