Who rebuilds engine on a GT5000]

These are always lawnmower repair shops in every area. Just do a google search of lawnmower repair shops in your city. Most places would just swap a new motor rather then rebuilding it. They can also check it to see if a motor is actually what u need and not just a tune up and oil change. When oil isn't changed it gets thin and makes the motor smoke. Hopefully new oil and filter is all u need good luck.