yeah the spektrum & decent servo like the 645mg would be a great upgrade. You could also get a good FM as well but I presonally love the spektrum as you virtually elliminate all glitches and you'l never have any problems with freq clashes.

A new radio & servo will make drastic differences to your steering but the buggys adjustments dont end there. There are many other asjustments that affect steering & cornering. If your radio controller has a dual rate(D/R) dial on it you can turn this up to increase the steering throw. Ideally the rear wheels should be slightly toe pointing in and the front wheels slightly toe out. Also try playing with the different steering akcerman bar positions with the steering rods. This will also help the steering turning circle making it more or less servere. As you start to learn more, you'll also start to tinker with the suspension and brake settings which also play a large part in cornering. Cornering is a fine art and requires considerable driver skill along with having the right buggy setup.

Dont be scared to ask around for advice at your local track. whilst you'll always get some that are not willing to help there will be many who will be more than happy to give you a helping hand.

Good luck!