Soft Feel

Do I need to connect the power cable that came with the video card somewhere in The MAC Pro to get the card to display video ?

Yes.

Does the existing display port support an older Cinema Display, vintage 2008, or do I need to use the adapter that came with the package to light up the display ?

You will need either single link or dual-link DVI adapter probably.
The install guide is right there on Nvidia.
And all the details that I posted a couple days ago on Feb 6th (Sunday):
FYI for Quadro 4000 Mac Owners upgrading to 10.6.6:

To save you a lot of clicks (the doc links to the nvidia product page) - here's the page with the current (as of this AM) Quadro OS X 10.6.5 Driver page shows the 11/16/2010 driver date/v256.01.00f03. But the file downloaded is 'Retail_256.01.00f03v5.dmg' (28.9MB) - dated Dec 17th.

http://www.xlr8yourmac.com/archives/jan11/010611.html#quadro4000
http://support.apple.com/kb/HT4499
http://www.nvidia.com/object/quadro-macosx-256.01.00f03-driver.html
Reinstall the 10.6.6 combo update manually is sometimes a good idea (some of us use only combo updates when it comes time to update OS X).
Here: http://support.apple.com/kb/DL1349
From Nvidia:
Mac OS X Software Version Upgrade
Make sure your Mac Pro software version is 10.6.5 or greater. It is important that you check this first before you install the Quadro 4000 for Mac graphics board.
If your system OS X is not at 10.6.5 or later, you need to upgrade.
10.6.6: http://support.apple.com/kb/DL1349
Use the following procedure to get your system OS upgraded to 10.6.5.
1. Click on the Apple icon in the upper left corner of the screen and select Software Update...
2. Continue to install software updates until your system OS is reported to be 10.6.5 or later.
Mac Driver Upgrade
You will also need to install a driver package to be able to run your Quadro 4000 for Mac.
The driver package is included in the CD that ships with your product. Please follow the installation guide for further instructions. It is also available for download at the nvidia.com driver here.
Important: Both the Mac OS X Software version upgrade and the Mac driver upgrade must be completed before installing hardware.
Please note that the downloaded file will be a single file that includes both the graphics driver and the CUDA driver.
http://www.nvidia.com/Download/index5.aspx