There are many routes to go for new rigging. I'd simply suggest buying all new stuff from Murrays. They'll have the lengths listed in their database. I bought new rigging for my 5.7M from Murrays, and I don't remember it being expensive.

Alternatively, you can get the lengths needed from Murrays, and go to your local West Marine and make your own rigging right there in the store.

You don't have to have the front trampoline on to use the boat. If you eventually have to replace the front trampoline, I'd advise you to go with an open weave "bow net" style instead of the trampoline. It makes it easier to tie things down, and gives the wind less to push against. My 5.7M and my friend's 5.0M were both flipped on the beach during a storm, while the P19 sitting with them never moved.