Jacob's recommendation on tuning P first is exactly what you should do. We've used PID controllers for the past 5 years, and used just P control on almost all of them. There are several good white papers on CD about PID, including one by Matt Krass. Greg's suggestion of plotting the values is a good one. One way to get the step input is to change the setpoint. See also, the following excerpt from the PID article on wikipedia:
http://en.wikipedia.org/wiki/PID_con...#Manual_tuning. Once you understand the manual process, you could try to play around with autotuning:
http://forums.usfirst.org/showthread.php?t=10555
The example was optimized for driving on the regolith, so there's a few things you'd probably want to change for driving a turret.
The first thing I'd do is remove the PID rate limiter. This was designed to keep the wheels from slipping. Hopefully your turret doesn't have that problem. Leaving that in there will slow down the response and make it more likely to oscillate.
I'd also replace the robot drive VIs with the motor control VIs. Since you aren't using the features of robot drive, I'd go with the lower overhead.
You mentioned using a Victor speed controller. I'd highly recommend using a jaguar. It will give a more linear response (PID is designed for linear systems). It also gives you much better slow speed control, which will help in reducing the oscillations.
http://forums.usfirst.org/showthread.php?t=10182