Hi other Nathan (lol)
You won't need the 12 tooth pinion gear if you are using the VersaPlanetary. You should know that these gearboxes are not actually designed to work with CIMs and MiniCims, some modification is necessary (I am not sure what you have to do but I bet you could find it by searching CD) I am suprised no one mentioned the P80 gearbox.
http://banebots.com/c/P80K-S4 (the grease and CIM mounting kit are wirth it for $12 more) I would recomend this over the VersaPlanetary for a CIM to wheel drive robot as these gearboxes are designed for CIM style motors and are much beefier. You are also going to need a battery, here is the standard FRC battery.
http://www.andymark.com/product-p/am-0844.htm You are going to need a battery charger, and it would probably be a good idea to put breakers in your circut so you don't fry things.
I you are scaling up to a car I would recommend these wheels
http://www.andymark.com/Pneumatic-Wheel-s/309.htm and if you take my sugestion and use the banebots gearbox you will need this hub for that wheel
http://www.andymark.com/product-p/am-0077a.htm
If you use the versaplanetary you will need a wheel with a hex hub. The wheel you selected has a bearing in it, this would be used if you were driving the wheel with a sprocket and chain (or belt) and the wheel was spinning on a dead axle and from your simple CAD it doesn't look like you are doing that.