How long it takes you to buy it is your choice (one big order saves on shipping!) but you'll want to open your mechbox as few times as possible. I'd personally go with getting the parts at whatever pace you see fit, but wait until you have them all before swapping so you can do it all at once.

do you guys know if the cabalas kraken has the v3 gearbox?

All AKs and AK varients have a version 3 mechbox.

This may sound like a stupid question but where do the bushings and shims go?

Hmm. I'm thinking you should try and meet up with some local players to get them to show you around a mechbox. Trust me, it will be worth it.

Also check out the videos on www.mechbox.com

But to answer your question, the bushings go in the holes on the side of the mechbox. They're the things the gear axles turn in. The shims are very small spacers that go on the gear axles to make sure the gears are spaced properly.

What's the difference between a piston with full teeth and a piston with half teeth?

Ok dude, seriously, you need to start doing some of your own research. Even a simple google picture search would answer that for you... unless your question was what are they used for, because that's actually a good newbie question. Half-teeth pistons are used with helical gearsets. Full teeth pistons are used with normal gears.

There is literally TONS of information on different mechbox components scattered throughout the internet. If you don't know any of this stuff, stick around for a while and READ.

Some suggested sites:
mechbox.com
airsoft retreat
arnies airsoft
airsoft canada

Thanks for the sites, I allready watched the ak dissasembly video and the mechbox dissasembly video on mechbox, and I allready knew the obvious about half tooth and full tooth pistons, I was wondering what they are used for.

I believe the time has come for the hand holding to cease.
Its time to let the new entry level airsofter to try and fly on his own and find his own means.

yjb63, this website has a wealth of information through out its its multiple sections. Please feel free to use the search function to try and find answers to any questions you may have. Although we do have this newbie section for asking questions, many of the questions you have right now have already been answered in the past. Just poke around, Im sure you will find alot of info and enough reading to keep you occupied for a while.