You can start a terminal window and issue the following command:
if the last part of the output is RELEASE_I386 i386 then you use the 32bit version. Otherwise, if you see X86_64 you use 64 bit
To my knowledge, that is not the way to find whether you run the 32bit or 64bit Finder. This command will show whether your Mac booted with the 32bit or 64bit kernel. All current Macs, except xserve, boot by default with the 32bit kernel. Holding the "6" and "4" keys will force booting with the 64bit kernel if the Mac is 64bit capable.
Most Intel Macs, when running the 32bit kernel, will run both 32bit and 64bit applications. When both versions are available the 64bit version will run by default, like the the 64bit Finder. Only early Intel Macs will only run 32bit applications and cannot be forced to boot with the 64bit kernel.
However, apparently the 64bit Finder is not a problem for SheepShaver.
Where you write "I needed to create a file called "shared" in my SheepShaver folder", I suppose you meant a folder called "shared". That folder can be anywhere, but when it is not in the same folder with SheepShaver you need to enter its full path in preferences instead of only its name.
(The manual was written for the full July 2008 download that contains the shared folder inside the SheepShaver folder as well as a keycodes file.)