Remote desktop help

I'm not sure about an Apple-specific solution for off-network screen sharing. What I do know: Skype will let you see your dad's desktop, and then you can walk him through the steps of what do to on his desktop.

 

I use TeamViewer, which is free for personal use and works with Windows, Mac OS X, Linux, Ubuntu, iPhone, iPad, etc. It's very secure and quite simple to set up and use (no messing around with ports), which comes in handy if providing remote support to those who aren't very computer literate. You can talk them through the setup on their end and be connected to them in less than a minute. I prefer it over LogMeIn because it includes free file transfers between computers, a feature I use frequently.