Line Follower w/ object detection

I am working on a project, and would appreciate some help.
As the subject says, the goal is to build an autonomous line follower that can also search for an object (a.k.a. navigate a line course and at the end maneuver towards an object to end the course.) What I was wondering was if the parts we have (and want to buy) will work for this project. What we have right now is

Arduino Mega 1x
Treads instead of Wheels 1x (http://goo.gl/TBmA0)
Twin motor gear box 1x (http://goo.gl/LFoyX)
PWM Motor Controller 1x (http://goo.gl/veCxE)
Ultrasonic Sensor 2x (http://goo.gl/bwxvT)
Light sensor Array (http://goo.gl/2j1q0)

This will constitute a majority of our robot. The motors will be hooked up to the PWM controller, which will be wired to the Arduino mega. The ultra sonic sensors will be in the front of the robot, facing forward at an angle so that there is a ‘focal’ point of ultrasonic waves. My question is whether the parts and layout I described would work as a robot, and how many ports would this use in the Arduino chip. A second, not as important, question I had is how would the wiring work for this (e.g. PWM controller would be wired to a Digital port, ect.) Thanks

I think you're missing a power supply, and some software, and of course the chassis and wiring and bearings and so on to connect that lot together to make a vehicle. Otherwise, what you have there looks like a kit of parts that could form the basis of a robot doing what you describe.

I think you're miss some thing on your motor is operate at 3V but the PWM Motor Controller is operate at 12V to 55V, so it can not work with 3V motors.