If the liner is faded and wrinkled but still sound (or at least patchable), then you don't need to worry about liner fade from chlorine and can hammer the FC up to 30 or 35, no problem. All that will happen is the liner may fade some more. I'd get pH down to 7.2-7.4 because chlorine is more effective when pH is lower.

Plumbing leaks can be tougher. Are the pipes PVC, hoses or flexible PVC (TigerFlex)? Pool builders regularly use internal barbed fittings in TigerFlex and they ALWAYS leak--proper Schedule 40 glued-on fittings, same as used on regular PVC, are what work. Any other internal fittings should be checked for leaks too, as well as quick connects and any screwed on fittings. Car mechanics have classically looked for leaks in tires with a mixture of liquid detergent and water. Won't hurt plumbing lines.