You know, seriously, everything you asked could be answered yourself if you read through that Tweakheads site and search this forum (and Google, too). But since you're asking to be spoonfed, and I'm not doing anything important right now anyways, I'll toss out some basic info that might help you.
You have two general options on what way to go on getting into making music: HARDWARE or SOFTWARE. There are advantages to each, but obviously on this forum you're gonna find that most folks have chosen the hardware route. Personally, I tried software first but just couldn't wrap myself around it, so I went the hardware route instead. You gotta decide for yourself which way you wanna go.
If you do choose the hardware route, you're still likely gonna interface with a computer eventually, but your primary music making will happen on the MPC (probably, maybe, but not necessarily). For that, you'll need to start off with a minimum of an MPC and some way to hear what you're doing--that could be monitors (self-powered studio speakers) or at the most basic level, a pair of headphones.
In addition to the MPC and monitors/headphones, if you're planning on sampling, you'll need some sort of sample source. That could damn near be anything: turntable, CD player, iPod, a home stereo, DVD player...basically, anything that has outputs can be connected via some sort of cable to the 1/4" ins on the MPC. You'll find that most hip hop producers that use MPCs sample from a turntable (likely plugged in to a DJ mixer, which then plugs into the MPC) but that's more preference than anything else. Why? Because it sounds right, that's why.
You also might want to add in a MIDI keyboard of some sort. If you do, you're gonna need one that (A) does MIDI and (B) has sound outputs. You'll need to read up on MIDI if you wanna do that; just remember that MIDI isn't audio, it's just data that the MPC reads, so you need the audio routed somewhere else--likely, a mixer of some sort (and probably not the DJ mixer on the turntable--but maybe if you wanted). Then you'll need to also connect your monitors to that mixer, and your MPC as well, so all your sound from all your equipment is coming out of the monitors.
Then, if you want to RECORD what you're doing on the MPC somewhere (besides resampling) you're probably gonna want to connect your MPC to your computer to record into DAW software, like ProTools, Logic, Cubase, or whatever. To do that, you'll need to connect the outputs of the MPC or your mixer or however you've got it setup to some kind of inputs on your computer. A good way to do that is with an audio interface, generally some sort of multi-input device like a standalone Presonus unit or a big sound card. Each input will correspond with a TRACK in your DAW software.
And all that's just scratching the surface. There are a million things you could do, and a million ways to do it. There aren't a whole lot of simple answers to any of this because there are a TON of variables involved. How one person sets up their equipment and how they use it is gonna be completely different than another person.
Now that that spoon out your mouth and start doing some research.
