I'm bored. I've been under house arrest for two days and I want to "play" with some remixing of my own.

I've just listened to SGT Slick's Gimme Gimme Gimme, and believe it or not, ABBA is where I'd like to start to "modernise". It's really simple (and the haters are going to hate), but I play a lot of ABBA and I'd like it to be punchier.

Here's the question though....how do you get the tracks in different layers (if that makes sense), and add your own bass line/beats?
I seem to remember you could buy the "stems" from somewhere....anyone got any ideas of where?