Welcome to rollaclub. May I suggest reading the rollaclub wiki (link at top of page), as it's chock full of k motor goodness. Research before posting is usually the go first, but I'll humour you :P and answer the best I can.
I hope your heater works really well. :P
You really need to know the specs for things like tappet settings, spring settings, etc. There should hopefully be a grind number on the end of the cam. If there is, ring/ email Kelford and get the specs.
I assume that's do nothing. Yes they do something. No, they don't do a lot. A big port head and a shave will get you some good-ish neddies, but someone who knows what they're doing will get more out of a small port head.
No, but they do disintergrate after a period of time. I won't use them.
I've usually had side dafts of some sort, and I use socks on the twin cam, and sandwich filters on the 3/4K. Never seen the need for a CAI set-up. (You live in New Zealand, the whole country is a CAI set-up.)
Why?
What do you want it to do? What are you going to use it for? Only you can decide whether it's worth it or not. Can't help wih the 4AG price, never done one.
Before you post again, have a read of this: http://www.rollaclub.com/faq/index.php?title=Main_Page
Cheers
R