I believe there isn't a huge difference in the costs between beaings unless you are buying a set in a Honda box. Bearings have to comply to international technical standards so you are pretty safe certainly if you stick with big names like SKF, Timken, NSK etc. if you can read the bearing size from one of the races then it's possible to go in to a bearing stockist like
http://www.bearing-supplies.co.uk/index.html
and get what you need.
As far as doing the job is concerned, it shouldn't be any more difficult than say changing the wheel bearings on a car, however, if you think you might not have all the tools or the confidence, any decent workshop should be able to do it. Not the best person to advise, although I'm an engineer, I haven't done this in over 30 yrs so not on a modern bike, though how much can headstock bearings have changed

.
Did it recently on my 03 with 60k kliks on it and it made a big difference, so much so that I nearly dropped her pulling away from the workshop

, suggest getting the forks flushed out and new oil at the same time.