direction, speed control with PIC?

i want to build a car is able to follow a light source by using PIC16F877.the car must be able to turn direction when it detects the light source and follow the light source.the angle of turning is not important, as long as i can finally get to the light source.
(1) what motor should i use?servo or stepper?and how to control the direction with the PIC?
(2)how to control the speed of the dc motor with the PIC?

can anyone tell me how to implement it in detail?

(2) keep sending the pulse to the motor, whenever the pulse width is long, the speed will increase as well.

Try look at some Hobbyist/Robotics sites.Light seeking robots are a common project, you should be able to find info and example code fairly easy