Best thing I can say is hunt around the remixing forums on OCR. Maybe pop a question or two, you might get lucky enough to find a response. (just don't mention the illegalities hehe) There's a -shitload- of info to be had in those forums, so it might take some time to find what you need. Hopefully that will point you in the right direction.
http://www.ocremix.org/phpBB2/viewforum.php?f=7
(they also have a nice Fruityloops (FL Studio) tutorial thread. The thing's almost a damn textbook lol.
Also, for starters, I don't know about isolating/ripping vocals from mp3s but as far as most the other remixing features, FL Studio (the latest versions) work well with mp3 samples/tracks etc. Although it may take some time to learn how to use everything to do whatcha want to do. I think FL Studio 6 is slated for a release sometime soon, if it's not already out. It's a good solid program for getting your feet wet.
Also: FL Studio works with VSTi's as well, and there's a lot of free VSTi's that might accomplish some of the remixing effects you're looking for. i.e. turntables, scratches, etc. etc. Though many VSTi's require some tweaking for the desired effect, i.e. don't use the presets, except as a kinda guideline.
Happy hunting, and welcome to the long yet fruitful road of remixing and sequencing. *grin*