I'm not sure how long fly line lasts or how often you should replace it. I would say start fresh, even if it's not going to break on you, it will probably have some permanent memory from being on the reel for so long.
As far as knots, this website helped me out a ton when I first picked up a fly rod. http://www.flyfishingforbeginners.com/techniques/knots/
Good luck man, that rod and reel is plenty for redfish, they're a blast to catch!
As far as knots, this website helped me out a ton when I first picked up a fly rod. http://www.flyfishingforbeginners.com/techniques/knots/
Good luck man, that rod and reel is plenty for redfish, they're a blast to catch!