Upgrading from Windows 7 Pro 32-bit to Windows 7 Pro 64-bit

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You will have to do a clean installation, there is no in place upgrade path from Windows 7 32 Bit to 64 bit.

Using the Windows 7 64 bit disk, install the Windows 7 Windows Easy Transfer Utility from the DVD (To find it, just navigate to x:\support\migwiz, 'x:' represents the name of your disk drive. In this folder, you will see a collection of files, the important one you need to look for and double click is 'migsetup'.) , run it and create a WET file (Windows Easy Transfer file), if you have an external hard disk, you can have it stored there so you can access it later when you do a clean install of Windows 7 64 bit disk.

Once you have done that, simply do a clean install of Windows 7 64 bit disk. In Windows 7 64 bit disk, launch Windows Easy Transfer, follow the on screen wizard, point to where you stored the the WET file (external hard disk), and it will restore your personal files and settings. Reinstall any necessary applications.

If you have an OEM version of Windows (Pre-installed Operating System), you will need to contact your computer manufacturer and request a set of recovery disks.

http://www.notebooks.com/2009/10/07/using-windows-easy-transfer-in-windows-7/

Retail copies of Windows 7 include both 32bit and 64bit disks.  If the copy you bought only had one dvd then you did not buy a retail copy but an OEM System Builder copy.  OEM copies do not entitle the purchaser to both versions of the software.  You need to purchase an upgrade license retail copy (or full license copy) of Windows 7 Professional.  Anytime Upgrade does NOT enable you to change from 32bits to 64bits.  You must use retail to change between architectures.

In the Windows 7 Professional 64-bit "Upgrade" disc the same as the retail Windows 7 Pro 64-bit version, or is there a difference?

Yes, all retail Professional dvds are the same.  It is the product key that determines whethere it is a full license or upgrade license.  Regardless of which type of product key it is, the software installed is exactly the same Windows 7 Professional.

"I heard that there is a chance that I could have someone (Microsoft) send me a 64-bit version since they key will work for either version"

What you heard pertained only to Vista.  Vista retail editions below Ultimate only contained a 32bit dvd and purchasers had to order a 64bit dvd from Microsoft for $10 shipping and handling.  That does not apply to Windows 7.  All retail editions of Windows 7 include both dvds.  Since you did not purchase a retail edition, Microsoft would refer you to the OEM for any assistance.  Since there was no OEM you are out of luck.  That's why an end user should not purchase OEM software directly.