Plums - DO IT, just watch his age, you can't compete till he's 18months (from memory) although you can enter at an earlier age but won't record a time, just be careful because its hard on young joints and you don't want to build up any inherent weakness
I start early with useful things, wait command is good (getting a solid wait with distance between you and your dog), the other things to do early are get the dog to chase something like a tennis ball, the other thing is target training, I.e. bit of something (like a butter tub lid) put food on it, after a bit treat when they touch the target, gradually build up time between target touch and treat, this will make contact training so very much easier
At about 14months I start on jumps and stuff, some do it earlier, some later but it works for me
You'll also need to get him KC registered as an activity dog £15, to compete hat is, then he'll need measuring by a measurer £4, and he'll need a book £1.50, Julie's getting measured tonight! Then he'll need measuring again ( think that's within 24 months)
You WILL get fitter, you will also (hopefully) find your dog is much faster than you, then you will find as I have that teaching 2off 2on position on a contact with a wait is the only way you can catch up with your dog who is just too fast, generally if we get a clear round we will place in top 3, more often than not we just get in a mess because I'm too far behind and we get dq'd