RE: Sail material
It depends on what your ultimate goal is. If you're cutting sails for a strict static display, dacron is the probably the best choice. If however you plan on actually sailing, and more specfically, competing with the boat, I would definitly advise you to have them professionally made, unless you have a home builder nearby to assist you in cutting and broad-seaming.
I have a couple of articles posted in my Northwind Group at yahoo. In the files section (you'll have to join the group to read) there is a folder on "Sailmaking".
[link=http://groups.yahoo.com/group/Northwind36-600/]Northwind 36-600[/link]
To cut sails that are efficient will require a camber board which can be homemade. But by the time you build the board, obtain all the materials, it's going to end up being far easier to have them cut for you unless you've got someone who knows what their doing to help you out.
As to the actual sail material, quite a few choices her. Mica film works fine on smaller boats, but creases easily. The fabric of choice these days is Trispi. This is a transparent mylar with re-inforcements imbedded in the material, comes in 25, 40 and 75 weights. (higher being stronger). Two other good materials are synthetic fabrics "Icarex" and "Toray" These come in many different colors.
I've included a link for these items where a lot of us EC12rs obtain it. Trispi is listed under films, Icarex (being phased out for the newer Toray) are in the fabrics section
[link=http://www.citystar.com/hang-em-high/]Hang-Em-High [/link]
Hope this helps
Chris