Well, I can't say anything about PID Classes, but I can explain the concepts of PID to you.
First, look up the paper "PID without a PHD", read it over and over until you understand it. It helps to work examples of the kind of numbers you might see on paper.
Whether the motor burns out or not is unrelated to PID. That concerns motor thermal load. Some motors can be held at stall for a long time, some motors will smoke in a few seconds.
For a PID loop to work, you must sense the controlled parameter - height of your fork in this case. Figure out how you're going to do that first.
Then just try a simple P loop, and use fixed values instead of variables for development.
For example: Make the fork go to 4 feet. Let's say P_Factor = 50, and the max range of the fork is 0 to 8 feet (for this example, to prevent value over-runs), and (Motor_speed) is a value from 0 to 255 that you send to the Jaguar, where 0 is full reverse, 255 is full forward, and 127 is neutral.
Code:
(Delta)=(actual_height-4)
(Motor_speed)=((Delta)*(P_Factor))+127
Work that example on paper (or in your head) with a few starting heights to see what happens.
Write back with more questions.