You can do an 32 bit to 64 bit upgrade via licensing requirements. In other words if you have a 32 bit version of Windows you can buy and install an "upgrade" version of 64 bit Windows. But what happens is the new version will save your old 32 bit version back into a folder, and then do a completely new install of the 64 bit OS version. The reason is because the 32 bit kernel is not compatible with the 64 bit kernel for upgrading purposes. You will have to reinstall all your programs, it will be a fresh new installation.
Note that 32 bit programs run fine under a 64 bit OS. If you have problems with any programs running, it will be a conflict within the OS its self, it will not have anything to do with it being 32 program running under a 64 bit OS. If a program gives you an error message when you try to launch it, or it refuses to launch at all, it would very likely do the same thing if the new OS you just installed was the 32 bit version as well.
As mentioned though, Windows 8 is still beta, and people are reporting a lot of bugs and programs simply do not work with it.....yet. I am sure by the time the final release is available, there will be much more support and the bugs will be fixed.
It is HUGELY advisable that if you do want to run Windows 8, you do it as a secondary install for a dual boot and leave your old Windows installation active and usable for now, as you are going to have issues of some kind, we guarantee it.