new aussie jib system might be convenient; won't invest in new sails when you intend to buy another H16 next year. Same for Harken 6:1 set. When the actual set works cope with it. Replacing rudders to my opinion doesn't make sence neither unless they are seriously damaged. Mind: they are available in various types and quite expensive - especially when considering to chnane cat next year.
I started on a 1992 H16 and I'm still using it. Technically it's OK but not new. Most important: get the feeling for cat-sailing and have fun. You'll gain experience quite fast and when something goes wrong it's old stuff so won't that hard. By the way: The Hobie 16 is one of the strongest cats I know. Almost indestructible (unless you hit a steel vessel see other topic..) Good luck !