How to back up a buggered up MacBook?

[3become4]

Right, so my MIL poured spilt a cup of tea on my MacBook.

When I last checked (and it's been a while) it would turn on and off and mostly work. Except for the keyboard and track pad which are buggered. So it doesn't really work at all unless you plug in a keyboard and mouse. I'm planning on taking it to the Genius bar for them to work their genius on. But I assume I should back it up first? I have no idea how to do this or if I can do this when it's not really operating properly. Can I just send everything to the Cloud? I have no idea what the Cloud is mind you...

Um. Help. Please?

Ah... do I need to get an external hard drive like on the other thread? Will that work if I need to plug a mouse in (although just checked and track pad might be working)?

Get an external hard disk. Plug a mouse in, set up time machine and choose the external drive as the disk you want everything to be backed up onto.

Aha. I did always wonder what time machine was...!

So, really that simple? Thank you so much.

I don't suppose you have any idea of whether or not my MacBook is likely to recover from Tea-gate? It's running slowly at times and the key board doesn't work (it only types question marks in little boxes!) but it hasn't exploded yet!