Measureing the crank is quite simple if you follow the guide lines in the service manual. It pretty much tells you where to sit it on blocks, where to measure, and the 'out of true' tolerence.
If it's out of spec it's not a complete disaster as the webs can be teased back into position with a precision tool. I use a carefully calibrated bloody great big copper hammer.
What I do is measure the crank as is, then give it a gentle whack and see how far it moves. If it goes right past where I wanted it and a good way beyond then I'll be prepared to bin the crank as it generally means that the crank has lost it's mojo and it'll move again first time it's back in the mota.
If it's a good 'un then I'll pop it back in the blocks and measure seven points and note down the runout. This helps me determine the shape of the crank compared to it's 'true' centre line. I'll then bash it about until it's as true as I can get it.
Honda give you a huge tolerence as you can see on the Techy bit. And if your cranks actually on the limit you can quite easily see it wobble around on the blocks.
The cranks are not that bad out of the box, and 99 times out of 100 are within spec, but they can be trued a lot closer. A well trued crank will give more power, smoother acceleration and a higher rev ceiling 'cos it's not losing all it's energy jumping around.
Difficult to say how long it takes to do as every crank's different. In the best case it could be half an hour, but I've spent well over that in the quest for the best.