PID help

[Skyehawk]

I am aware that PID threads are pretty common here on CD, and I have read most of them, unfortunately I am stuck in a college dorm and lack the ability to give this code a whirl.

Code: http://i.imgur.com/rJsdpB6.png

This is my periodic tasks. I am using a loop to check where our lifter mechanism is located (via THIS encoder, I have the right numbers for it to return inches), I am wondering if I have all I need here to get a basic PID running.

Here is how I plan to tune it (provided the code is fine):
My first step in tuning would be to set the P to about .25 (small enough?) I would have I and D at zero. After I reached a point of instability I would back off on Proportional a little and add in some Integral. I only plan on this being a PI controller, as I don't believe I will need any Derivative. Does this sound like the right tuning method?

Thanks for any help!