Remote Admin is another good tool.
Has all the features a standard trojan has...but it's not a trojan
Also lets you see the other computers screen in "real time" and control the mouse. It works surprisingly fast even on slow connections. It only updates the part of the screens that have changed...so just make sure not to run movies or anything if your on a modem

That's what we used to administer our windows server.

Linux or Windows? I'd use nc, telnet, (NOT R Services!!!), ssh (good idea) or any other good network communication program. Try talking to your sysadmin, what you're doing is most probably illegal though.