Most tools are standard like screwdrivers and allens. You will however need a couple special tools. One for the clutch adjustment, pinion gear install and removal. Glow plug wrench.
If you can and I recommend it as it comes with most of the common tools used on nitro touring cars, get the Hudy Set for Nitro Touring cars
Then get yourself a bottle of BLUE locktite. Do not use the red, you want to be able to remove everything.
Your radio will work, but you need a compatable receiver from Spektrum and bind it. You can program the radio for each vehicle separately. You could purchase a faster radio if you plan to get into racing competitively as the DX3S is a sport system and not really a race system. Not necessary unless you really want to get into competition. If you want to upgrade everything there's lots of options. Spektrum makes a DX3R or you can look at something like a Ko Propo EX-10 which is what I use. This is going to be preference. You'd have to feel the radios in your hand.
Servos, this is where I ask how competitive are you planning to be? If you are going to be competing in more than club level races then I'd recommend something fast. I like Futaba servos for on-road. The S9351
is a good digital high speed servo. For something more economical take a look at the S3305
servo. The 3305 is the most economical, about $35 a piece. That's what I use because I am not a good enough driver to get the most out of the higher speed servos. They've lasted a long time for me and always have worked flawlessly in my V-One RRR. Any manufacturer makes servos that would be just fine. Hitec, JR, Ace, Orion, Futaba, even spektrum makes some decent ones. Check out the numbers. They are rated in oz for torque and how long it takes the servo to move 60deg. A fast servo will mofr 60deg in .08 to .13 sec @ 6v. That's faster than normal human reaction time but you will never be limited by the speed of the servo that way.
Diff and Shock oil...this is where things get tricky because it changes the way the car drives. Personally I use Serpent oil (perhaps xceed brand now) in the shocks. I use 700cst shock oil all around to keep things pretty neutral(not too hard not too light). Oil is rated in centerstrokes (cst) and the lower the number the thinner the oil so the shocks will be a bit softer. This works the same with diffs too. Diff oil is a lot thicker than shock oil so do not confuse the two.