The GH Chassi is made by GH Hobby:
This chassis is 2 ounces lighter then stock chassis and alot stiffer.
The fix is not necessary you can do what chorner suggested and it works fine as well.
Clamping hex hubs are a must, Yokomo makes a nice set for the car.
You will probably also want to upgrade your drive shaft. As well as probably wanting to get some swaybars.
As for a RX battery, 1100maH NiMH should be fine. Should last you 3 5 minute qualifiers and a 20 to 30 main easily. The Duratrak Intellipeak Digital Pulse charger is perfect for these types of batteries. Not very expensive either.
One other thing you will want to do is to add 2 o-rings to the front side of the gas tank to elevate it a little more then the back. This will keep the tank from foaming up. You will have to use a little longer screw in the front. Just dont' tighten them down tight, just snug.