Greetings Steve Ruddy,
I never had your model tv, but I used to calibrate the TH50PX77U, which may be a similar model. If so, you will find a limited amount of options in the service menu. Before you begin, the first thing that you should do is to write down all of the service menu rgb settings before changing them.
In my tv, the only real settings that can be used in the service menu are the gains and cuts/bias. Then they have, if I recall correctly, an adjustment for all gains and all cuts, which are useful in adjusting the gamma level. The user menu settings for contrast (picture), brightness, and sharpness are sufficient for controlling these values.
When calibrating, adjust the rgb gain values then cuts/biases to obtain a proper rgb level on the graph for a D65 target for movie mode. Then look at the gamma curve, which for my model was around 1.9. You can using the ganging method to level out the gamma curve. Raising the allgain setting will lower the gamma curve between 50% and 100% IRE windows, and vice versa. Raising the allcuts setting will lower the gamma curve between 0% and 50% IRE windows, and vice versa.
There is also change your settings for adjusting the standard mode to D75, but this is another issue. Also, you may want to use the 10% Window patterns found on the Gamut Calibration Disk downloadable from this forum to adjust the settings with effects from the abl (automatic brightness limiters that decrease the picture level when it becomes too bright - energy saving feature in plasmas).
I may have FORgotten the proper descriptions of the settings, but I think that I am close enough for you to understand.