if the mesh is set correct you dont have to worry about stripping spur gears, cluch spring is normal on a car to break but you can upgrade using the traxxas 4146x spring. Header gaskets only cost a couple of bucks the most, traxxas and hpi .15 side exhaust gaskets will work or you can make your own out of gasket material you get from an auto parts store. How did you spend $400 trying to fix it? What did you replace?