Here are some resources for you:
vexforum.com (official vex forum... talks about every vex related stuff)
http://www.inpharmix.com/jps/PID_Con...ms_Robots.html
This is a very through article explaining beginning (1 light sensor) PID control for line following.
After you got that down, implement more light sensors to make it faster / accurate.
As for the gyro sensor, I'm pretty sure it should be put in an analog port, but I am not quiet sure how it can help with line following. I only use line sensors and they do a very good job following the line with PID.
Hope this helps.