for reasons that are too complicated to explain, I was thinking of buying an iBook and picking up an airport card to put in it later. Is this terribly difficult to do?
In my experience, it's ridiculously easy. I installed an Airport Extreme card in my 12" iBook about 5 days ago, and it took me more time to find a coin to unlock my battery than it did to install the card itself. Unlock the battery, lift off the keyboard, slot the card in and connect the antenna, clip it down, put the keyboard back, put the battery back, switch on, and hey presto! Up and running wirelessly.
It was incerdibly easy to do on my 12" iBook G4. The hardest part (in my opinion) was getting the keyboard back on... but it's back on and I never have to take it off again soooo... yeah. You won't break anything and if you do you don't deserve to have an iBook...