Good job so far bro! The quickest way to make it go forward is to change it in the remote settings. Go to mixer. Find the channel used to go forward and select it. Go to src (the thing used to select which knob does what) and press enter on it. It should have an ! (Example !AIL) Next to it to show that it is inverted. The graph on the screen will also be inverted.

And do you mean that motors spin faster or do you mean that they cover more distance? You should expect the latter as their circumference is larger Hense they will cover more ground.