Would it be worth the extra cost to replace a vinyl liner with a new gunite shell built inside old 15x30 pool or stick with the vermiculate bottom and a new liner since this one is 15 and leaking?

Think of it like this. This liner is 15 years old. How much is going to cost me to keep on fixing this one? How much is it going to cost me to put in a new one? More than likely, it will be cheaper to replace it. Good luck:)