To increase the rake, you have options. You could hack the neck off and weld it back on at a different angle, hopefully the shop you pick does a good job as there are safety concerns there if the do a poor job... Or you could find a set of raked triple trees. I'm not personally in favor of either method for my current bike, but some other project someday probably will go with option #1.
How difficult? Can you use a grinder, measure acurately and weld? I'd suggest making up some sort of a frame jig so that you could keep the neck square in relation to the rest of the frame.
