If after fixing the known issues your rudders still aren't perfectly straight, you can install one of these:
http://www.murrays.com/50-60400011.html I put one on my old 14 because the tiller arms were bent from a previous owner and I didn't feel like replacing them. It worked out well. As far as the stiff rudders go, get a BIG flathead screwdriver and you can loosen that up a bit. There's a plastic screw that tensions a spring that you can access from below the rudder casting. Unscrew it a bit to relieve a little of the rudder cam tension. You still want enough tension so the rudders lock in the up or down positions, but not so much you can't move them when you want to.