Re: a new neck . . . can I repair the old one?
My first tenor was a Jupiter, and through well-cared for use it still managed to drop a key during an audition. If you're serious about the sax, I might suggest a new horn. I've heard Jupiter's come a long way in the past few years, but I don't think I'll ever trust them. Unfortunately, getting a neck that truly fits often requires a custom neck to be made (which there are from notable names such as Phil Barone), which can get expensive. Good luck!