Yes, you need the spreader. I think it is actually made of the same extrusion as the 17 boom, which is a little smaller than the 14/16 boom material. It looks pretty hard to duplicate, so you probably will end up having to buy one.

I had a Sport and thought it was more fun to sail with the jib, but I really didn't see a lot of performance increase out of it. Also, the jib I had was Mylar and had a really short life span. I would recommend a Dacron one.

If you do the conversion, you can also add a Screacher or Hooter and still maintain the jib. I have one on my 14 and it makes a huge difference. You have to have a solid mast, though, or you stand to rip your comptip apart and solid 17 masts are getting hard to find.