Performance Catamaran built the 5.5 both uni and sloop rigged - a PC dealer should be able to help you with a jib kit for the boat. Any sailmaker should be able to make you a jib too although you'll probably find the price comparable to the dealer's price. If you have the long stays in front, you will probably have to install a new bridle and forestay as well.

With regards to the leak, there are several threads on here about locating leaks. However, in a nut shell, hook the output of a shopvac to the hulls so that it blows air into the hulls to slightly presurize them. Let the outlet leak - it's not that important to seal it tightly. Spray soapy water around all the fittings and the hull deck caps until something starts bubbling. If it is the gudgeons on the stern, you'll need to remove them, clean them, and reinstall them with some new sealant (3M 5200 or 4200 is great for this). Also be sure to spray on the inside of the daggerboard wells where the deck meets the daggerboard trunk because this is a common place to leak too.