Killua Zordik

I am playing as a shaper. I like to increase my "chance to hit". What do you think is more skill points-wise to spend, dexterity or missile weapons skill? Both of them increases "hit chance" but I don't know how many percent. I can see that missile weapons increases 5% chance to hit, but how about dexterity?

I'm moving in America by now. How do I register Blades of Avernum in the cheapest and easiest way ones it is released? Any step-by-step instruction?