You're going to be installing a new version of an OS, its always been better and std. practice to do a "fresh" install. This means NOT over the old install to reduce any conflicts, glitches or hassles you may encounter...period.
Next, doing a back-up will have to be done, that way your data or whatever is saved. You will also best served to clean your HD of current data, but that's your choice. When installing the new OS, it will format and do that anyways before installing. You offer no clue what your PC is, but if OEM type OS install, be sure to check their support website and query there. Most have guides to help you so its worth the trip.
While 64-bit OS will allow more ram to be addressed, you MUST search your manual to be 100% sure the total ram that can be installed. This is the other half, on the h/w side of things. Your PC or mtrbd. can handle x-amount of ram. Some systems may allow only so much even with the 64-bit installed, so check that.
Last, since this is Vista any possible offer to upgrade has long been gone, IMO. You can ask and see what can be done, but consider it past due. You may want to consider Win7 at 64-bit just to keep up to date as a passing thought of similar version.
I am upgrading from 32 to 64bit so that I can add more RAM for graphics programs, Photoshop, Painter12, LightRoom, etc. I am admittedly unlear of the path that I need to take.
Do I need to buy a new version of the software, do I qualify for the upgrade since I have the 32bit or it is already on my CD?
I also understand that I need to backup my current install, but do not understand why, will the 64bit not pull everything over, so to speak?