Windows 7 uprgading from 32bit to 64?

So I just finished building my gaming pc a week or two ago. I bought windows 7 home premium which came with both 32 and 64 bit installation disk I thought Installed 64-bit OS but I couldn't get any 64 bit drivers to work and always had to download the 32 bit software for it to work. I didn't think to much of it at first but after the second or 3rd time of not being able to install 64 bit driver (this time is was the xbox 360 accessory software) I decided to check "my computer properties and it says I'm running a 32-bit operating system. So, I guess I installed the wrong disk, ****! How hard is it to upgrade to 64 bit? I realize I will have to reinstall all my drivers, but is it fairly simple; can I still keep documents and installed programs, or will I have to start with a clean slate. I don't have a whole lot on this pc yet other than a dozen or so games installed only 3 or 4 of which I even play, but I really really, really don't want to have to reformat my hd I don't really want to reinstall windows either but realize I have to in order for it to be a 64 bit version.

What are the main benefits of running a 64-bit OS other than being able to run more RAM? I only have 4GB of ram right now, so would there even be any real benefit of installing 64-bit. So what's the difference between 32 and 64 and what does upgrading entail? Thanks for your help.