[jimmymc2286]

Fauxfox, I can understand your wanting a new buggy. The Hammerhead is a great buggy, so is the Trailmaster, both good choices. I'm not sure they are the best choice for you. You said you don't know how to work on the engine, or do the mods to the frame, or repairs that require more than bolt on parts.
You would be far better off keeping the Yerf Dog, and spending your money on some tools. For the price of a new buggy you can get all the tools you would need to build your own. With just a handful of wrenches you can rebuild a gy6. They are a very simple engine and you can find all the information you need right here.
You can buy a 110 volt mig welder from one of the discount stores for under $300 and in no time you will be welding like a pro. You can buy a used one for under $100. With a welder, angle grinder, tubing bender, and some time, there is nothing you can not build. Your age is not an issue. The only thing you have to decide is that you can do it.
The fact is your Yerf is not the best buggy, but with a little work and a lot less money than a new one it can be. When you are finished you still have the tools to build the next project.
Last thing. Building it if far better than buying it. No matter what it is.