If your dealer is firing it up for you, make sure he's plugging it into a high quality dedicated source -- ask him if he can hook it up to a blu-ray or hd-dvd player. Most definitely change the picture mode to "Cinema" and the color temperature to "Warm." Drop the contrast to maybe around +20 or so, and the brightness to about +8. Leave the blacks at "Light" and turn off color management. I can't give you a recommendation on the proper color and tint since they can often track quite differently -- I'd leave them both at 0 (the middle).
The 3 yr warranty is nice indeed, though keep in mind that Panasonic plasmas have a 2% failure rate, and Pio's are around 3% -- this technology is quite mature. So I would still propose that your choice should be between the 75U and the 5080, and the price difference is probably $500 between the two. The 5080 buys you better inputs (2 extra HDMI, 1 VGA), black levels, slightly better user-calibrated colors, processing, and a few extra features, but is usually 20-25% dimmer than the 75U.
Personally, when they were more like $1k apart in price, I chose the 75U. If I were instead buying today with a $500 difference, I'd probably spring for the Pioneer. But that's just me. The 75U is a fantastic plasma and I've been extremely happy with mine -- and certainly adding the ISF service menu calibration brings its color accuracy and greyscale tracking above what a 5080 can do without proper calibration.
As far as calibration goes -- if you get one done, you want someone who's ISF-certified and has the best equipment. Definitely not something that BB/CC people would do, and unless your dealer happens to be an ISF-certified tech, I would recommend searching for a professional calibrator in your area or finding someone who's acquired a good rep on the forums and seeing if they'll be touring in your area. I went with a guy who lives out in Ohio, but reguarly tours around the East coast/Midwest -- I just had to wait 3 months for him to get to the area.
That said, I would definitely recommend waiting until you have a blu-ray or hd-dvd player before considering a calibration -- it's something that really nails down the detail and depth in the picture, but I wouldn't spend so much on something like that unless you have a source that can really maximize your set's capabilities.