Not much need to break in anymore, burn-in is much less of a consideration with the new TV's then it used to be with the first and second gen plasmas. Spending $500 to have an $800 TV professionally calibrated seems like a waste to me.
1 - Don't ever put a plasma TV on it's side. They must be upright at all times. Keep this in mind when moving and unboxing.
2 - Once you get it plugged in and set up check the picture settings. Chances are it will be in what we like to call the factory set "torch mode", with the brightness and contrast jacked all the way up to make it stand out from the TV next to it in the store. Bring everything down do a moderate level.
3- Grab an AVIA or DVE disk:
http://myweb.accessus.net/~090/aviaorve.html
Enjoy your new TV!