Tony has given you great advice here.
While there are some similarities between snowboarding and windsurfing, do not be fooled into
thinking that the transition is going to be easy and simple.
Taking some lessons, on good beginner gear at a reputable school is the fastest and best way to
get started in windsurfing.
As Tony suggests, the school will have the right gear to get started on, but if you are a quick study/fast learner, you will want more advanced gear very quickly.
The boards you have mentioned are wonderful boards, AFTER you have several months of experience, but would be totally inappropriate to learn on.
Hope this helps,