If this has worked for 13 years, I would first get the ammprobe out and measure the amp draw. If the amp draw is what it should be, I would then take a look at the breaker. Breakers work on temperature. If there is a bad connection where the wire screws on the breaker or where the breaker connects to the buss bar it will cause the breaker to trip when it shouldn't.
Why do you have a 1 hp pump? How deep is your well? Can you get buy with a smaller pump and not change the wire? Is it possible your pump is going bad and not a wiring problem.
My well is 75 ft deep, water table at 30 ft and I get 12 gallons per minute with just a 1/2 hp pump. Uses a tick over 10 amps on 120v.