I have quite a few Ubuntu installations in the wild, set up for friends and clients. I support them all -- well, those of them that require support -- using
Gitso, which is a nice little front end to x11vnc and vncviewer, with connections tunnelled over ssh.
The only work that needs doing at the support end is to set one's router to forward port 5500 to the machine on which you'll be doing the remote support. Then it's just a case of running Gitso, switching the radio button to 'Give...