Hey,
I've never owned one either, but this is what I think you should do:
1. Learn how to load samples into it. If you only have the basic model, you probably only have a floppy drive...you'll have to grab one of your sample disks, pop it into the drive, and load the sounds into RAM. Hopefully they're in Akai format and will be already mapped out across the pads.
2. Once you have sounds loaded into RAM and you can trigger them with the pads, you're going to have to learn how to use the sequencer. The sequencer allows you to record notes that you play with the drum pads. Don't try to do too much at first; just learn how to get the notes in by pressing record and playing notes with your fingers , then play them back.
Next you'll probably want to learn how to edit the notes that get recorded; sometimes you won't play them exactly in time, or you may hit the wrong notes...you can edit all of this very easily I imagine.
After that, you may want to learn how to 'step sequence' which allows you manually enter notes where you want them.
3. After that, you may want to learn how to make your own samples. Grab som of your favorite records or cd's, plug them into the audio inputs of the Akai, then record small passages into RAM and map them across the pads. There's a little graphic interface on the sampler, you can fine tune your loops and individual hits with it.
4. Things to purchase to increase the value and functionality of your sampler:
You'll run out of memory VERY quickly if you only have 2mb of RAM, that is only 20 seconds of cd-quality audio. RAM is dirt cheap right now, you can probably max it out for less than $50, this will allow you to store large sample banks into memory and have more sounds at your fingertips .
Get some sort of hard drive for it. Loading from floppy disks is painfully slow, and you are limited to banks of only 1.4mb. I don't know what kind of drive it can take; you can go with either a scsi or ide drive. I'm sure that you can connect an external scsi drive to it, something like a small 4 or 8gb drive will keep you sample happy for a long time. If it takes internal drives, I would go that route because it's one less thing to worry about.
You could also maybe plug a ZIP drive into it. The older ones only hold 100mb, newer ones hold 250mb, and the latest ones hold (I think) about 650mb. the only advantage to these is that they are removable and you can bring them places with you...other than that, I don't see any immediate advantage to them.
And last, get a cd-rom drive. Most sample libraries come on cd nowadays, you'll need a cd drive if you want access to them. I think you'll have to get an external drive, probably a scsi drive which cost a little more than ide drives, plus the cost of the external casing.
5. Once you've taken care of the sampler itself, figure out a way to connect it to your computer. With a computer you can easily edit sounds record full songs into a wave editor to burn to cd, do detailed sequencing with a good sequencer software, create and edit samples before transferring them to the sampler instead of loading them from a floppy or other storage medium, etc.
You'll need to get a scsi card for you computer and a scsi cable to connect it to the sampler, as well as sample editing software which knows how to transfer the audio across the scsi cable into the sampler's memory.
Software used for sample editing and transfer: Recycle, SoundForge, Wave Surgeon, among others.
The sampler itself on the MPC is not terribly good by modern standards, but you can make it better by editing your programs and multis from a computer as well. I think Akai has a program called MESA which will do this.
6. READ THE MANUAL. I cannot stress this enough. Most everything will be documented in the manual, hopefully there will be some tutorials on how to do some of the things I've described above.
If you didn't get a manual with your sampler, you can download it here:
http://www.americanmusicsupply.com/manualfiles.asp?item=AKA+MPC2000XL
6. Check back here with your questions, there are a lot of smart people here who use them, I'm sure they'd be willing to help you out.
Take care,
Nick