Go with Babeths suggestion for your first trial bot .........perhaps 2 off battery operated drills?

That will initially solve your battery and motor problems... its also possible to use the inbuilt speed control and reversing switch.

Ask here ........ http://www.robowars.org/forum/index.phphttp://www.robowars.org/forum/index.php ..if you decide to go the cheap switching route.

OR if your pocket can stand it this speed controller does 2 motors and connects easily to the radio controller....

http://www.roguerobotics.com/store/index.php?main_page=product_info&cPath=61&products _id=132http://www.roguerobotics.com/store/i...o&cPath=61&pro ducts_id=132
More info here ...
http://www.robot-e.rdelectronics.co.uk/htm/md22tech.htmhttp://www.robot-e.rdelectronics.co.uk/htm/md22tech.htm