
You can sample anything you think you could make into your own. Sometimes you hear a song and think it would make a great sample, but start to work with it and realize it's not going anywhere. It's trial and error, with what works and doesn't. My pops has a hefty cassette collection so I sample alot from that. Within the actual music, I keep an ear out for piano and rhodes. That's my favorite shit to work with.
As for getting things off vinyl, You can do it a few ways. Usually you just get a turntable and a mixer which has a regular 3/4 inch output right into the MPC. As long as it has "Phono" as a preamp, then youre good. Once you have the section you want into the MPC, you make like a chef and slice and dice it up.
If you have a song on your computer, you first need to convert it to wav. Then you would need an interface so you can line out from your computer. I'm not sure exactly how the 1000 works, but you would set the MPC to sample which ever section of the file on your computer you want then go from there.