Welcome aboard Gramps. Lots of us here is one (Gramps). So it sounds like you're not terribly confident in your mechanical aptitude to fix this thing. Really, you have come to the right place. Can you change a flat tire on your car? Can you hang a picture on a wall? If you answered yes to these questions, then you can rebuild your grandsons go kart. Lots of knowledge on this forum, and with decent pictures and a explanation of what the problem is, we can get you through anything. Don't worry about what you paid for it. To your grandson it will be priceless and you will be the smartest person in the world. It's worth quite a bit when it's all said and done.