my advice would be to go if you can. The help you get at your first contest is worth more than a one-year practicing on your own in my opinion. You'll have fun, learn what you're doing right and wrong and make a bunch of great new friends. As for the plane I flew of the Venus II for my first year but there were sport planes like Ultra sticks,Sig Sr,Spot on and so on. I have yet to see in a contest to sportsman pilots fly their sequence twice.
P. S. You'll probably enjoy looking at other pilots plane setups also I know I learned a lot just from looking at their planes.