Hi Bob, welcome to the forum!
OK, I'll take a shot...
1. how many part are there. and what are they. please explain each part and what it does
The basic parts are the Kaleidescape Server, and the combination reader/player ("Movie Player 2"). You can have many players that all can play movies stored on your server. There's no (practical) limit to the number of players you can have, it depends how many rooms you want operational. But for the basics, let's assume you'll have a single Movie Player and a single server loaded up with some storage discs.
2. do you need a computer for this systemYou could use the system for its basic functionality without a computer (Playing movies and music). Technically speaking, a computer IS required during initial setup, but I imagine it's possible a dealer could come out and use his computer to get you set up and then he could disconnect his computer and you could happily use the system to load, store, and watch movies without a PC.
That said, I can't imagine anyone who was putting in a Kaleidescape who would NOT have a computer in the home. Having a computer on the same network lets you do a lot more organizing and is helpful in many ways... so I'd say it's highly recommended if not technically required.
3. if a computer is needed what are the requirementsYou don't need anything fancy, just a computer with a web browser on it, as the interface to Kaleidescape is done through web pages. If you want to do the synchronization of your Kaleidescape music library with iTunes, then the computer should be a PC, not a Mac (for now).
4. is it really the best system for the moneyAh... well, there's the tough one. Hard to really justify this kind of $$ to play movies and music, and of course the people on this forum are pretty biased, but do your own research and I think you'll find most Home Theater industry experts agree that it's the best PERFORMING system out there. Whether or not that means it's the best system "for the money" depends on your own needs and budget. We've all had people scoff at the thought of paying this much for a "fancy DVD player". Many will claim that you can do 80% of a Kaleidescape for 20% of the cost with some Windows Media Center solutions... (many of us might dispute that 80% claim, but that's another topic)... so if you're on a budget, then you should look into those systems. Many are happy with them.
For what it's worth, if you can afford a Kaleidescape, I don't think you'll regret it. On these forums, I've interacted with hundreds of owners and I've yet to find a single one who had buyers' remorse or found the system anything less than astounding and completely worth the money. I HAVE heard of owners of competing lower-priced systems that will admit to "Kaleidescape Envy" but take comfort in having spent so much less than did we. There's merit to that also.
I guess it's like asking if an Aston Martin or a Ferrari is "worth the money" when a Lexus or even a Toyota can do 80% (?) of the same thing for a tiny fraction of the cost. Many will scoff at a $200k-$300k car purchase, others will justify it as buying a finely engineered machine that performs at the top of what the industry can create. Both are probably right.
Hope that's helpful, good luck with your decisions. Feel free to post any follow-up questions for which we can be helpful.
--josh