Do I have to uninstall the 64-bit version first to be able to install the 32-bit version? I’m concerned about losing all my settings if I have to do that. I am wondering if it will just install on top of it, like when you do an upgrade.
Yes, you do. From the horse’s mouth:
Because you can’t do a side- by-side install, the 32-bit installer won’t even run unless you remove the 64-bit version first.
I generally recommend that people install the 32-bit version unless they have a compelling reason to install the 64-bit version. A large number of plug-ins and other extensions for Office only work with the 32-bit version (Excel, in particular, is prone to these issues because it has a lot of plug-ins).