New Dagu Rover 5 w/4 Motors, Encoders

Hi LMR

I just received my Dagu Rover 5 along with a Redboard controller (Sparkfun arduino) and Rover 5 Motor Controller, all from Sparkfun Electronics. I'm not looking to take over the world with an army of autonomous AI miracle machines, just start a fun hobby with my kids. We have just unboxed the stuff and haven't began any assembly.

First issue - there isn't a "top" to the Rover 5, but there are holes at each corner for mounting stuff. None of the holes align with the mounting holes on the electronics I bought. Is there a Dagu part that adds a deck to the Rover or am I meant to fabricate something to mount the electronics to?

Second issue (actually a question) - I bought the 4 motor version because 4 is better than 2, right? Now that I have it, it seems like a tracked vehicle with two drives per track is not an intuitive configuration because differential motor speeds could cause all sorts of havoc with the track. I suppose this is where the encoders come into play? Or is the 4 motor version better suited to a wheeled configuration? I like the look of those 60mm Wild Thumper wheels anyway :-)

Third question - Can I use an RC-style 7.2V NiMH battery pack instead of the 6 AA cells? What issues or problems might that present?

Finally - I have seen on these forums, and elsewhere on the web, references to a Rover 5 Explorer PCB. I haven't found a US source for this product, but it seems that it would solve my "deck" issue. However, it may only be suitable for the 2 motor version of the Rover. Does anyone know if there is a US supplier and, if so, would it work with my 4-motor Rover? I'd be tempted to buy another Rover (2 motor version) just for the convenience of this cool part if I could find one.

I'm a programmer and have some experience with coding for the Arduino, but sensors, motors, servos, and all the other electronic bits and pieces that combine to make a functional robot are new to me. Thanks for your help and input. 

Mulada