I am not finding the draw spec for the Viper motor, but most 1/8 brushless can pull around the 100 amp mark plus a bit for servos and receiver operations. That motor requires a 4 cell, or 4S as it's called, battery pack. To know if your battery will supply everything well, use this formula.
mah x C rating then divide by 1000.
This will tell you the approximate amp draw the battery will be safe to operate with.
i.e. a 5000 mah 4S battery with a 40C rating.
5000 x 40 = 200,000 divided by 1000 = 200 amps
Your motor can draw approximately 100 amps plus around 10% for servos. This pack will sufficiently meet your requirements.
Check online for your battery tray dimensions, then find a lipo supplier and see what packs they have that will fit your tray. If it's a bit smaller, you can take up the gap with a piece of foam.
Batteries can vary GREATLY in price. Maxamps, for example are pricey, but have good warranty and specs. But there are good batteries that don't cost a fortune if you aren't a hard core racer, like Turnigy nano-techs, Zippy flightmax, Gens Ace, and SPC plus many others.
Also watch where the wires come out of the battery. Some come directly from the end or the side and can interfere with how it sits in your tray, or rub the body or moving parts. Others come out of the top. Take a look at your kit and see which placement of wires will work best for you. Then add that to your search criteria.
As for chargers, the one Bill (cmnyj28) listed is a great little balance charger, and will take approximately 1 hour to properly balance charge a lipo. You can find others with more power, but most consider a 1C charge rate to be safe. So a 5000 mah battery would be ok to charge at 5 amps, a 3000 mah battery at 3 amps, etc. The AC6 listed I believe is a 5 amp max charger. The AC680 is a 6 amp and has a cooling fan for a bit more. These chargers also come with a variety of ends to charge different styles of batteries and different plugs. They also can work in AC or DC which is a nice option that not all chargers have. They don't need a separate power supply. Make sure, what ever you go with, is a Lipo BALANCE charger.
What's your budget for a steering servo? There are many to choose from.
That airtronics radio looks pretty decent for the price! I don't have any personal experience with it however.