First off, you can definitely get X running via SSH. Have a look at the so-called tunnelling capabilities of the ssh command that you access by appending it to the usual ssh invocation. Here's what the man page says: "ssh (SSH client) is a program for logging into a remote machine and for executing commands on a remote machine... X11 connections and arbitrary TCP/IP ports can also be forwarded over the secure channel". You might also check out how the '-X' flag to ssh works too, if you're working with X Windows.

Copying files from one system to another via ssh is even easier: check out the sftp secure version of the FTP program. It is quite scriptable (as I explore in Wicked Cool Shell Scripts) if you don't want to use it manually too.

Finally, in terms of setting up a secure-only login account, you'll want to turn off telnet access (see "inetd" or "xinetd") and give those folk regular login accounts: the only way they'll be able to connect will be via ssh.

Hope this helps you out!