definitely echo comments about doing the brakes and suspension first then the motor. Make it safe, then fast, so to speak. And doing the mods/upgrades to the suspension will help you get an appreciation for both the potential, and the limitations, of the car.

An interesting thing - if you start driving it with the stock motor and upgraded handling, you'll get a great opportunity to really fine tune your driving. When you haven't got bulk power to 'cover up' shortcomings in driving style, you have to learn corner exit and entry, braking application (smoothness in general) and turn in. All these things can only get better (and there isn't a single person here who couldn't get just a little better than they currently are, so I don't mean it as if 'you' yourself need more skill or something, I don't mean it like that at all!) then when you get to a motor with more grunt, you'll have a much better foundation to truly make the most of it.