FAT32 will work with no problems other than that a few rare data formats depend upon the resource fork and may thus not work correctly after being copied to a FAT32 drive, which doesn't support them.
You also won't be able to run Mac programs off a FAT32 drive.
You can dual-boot a Mac with Linux, if you really need to.
generic usb storage devices will simply mount on the desktop - you can drag songs directly from the iTunes window onto the drive (yay for global drag-and-drop).
If your salespeople are clueless, and, even worse, don't readily admit if they're not sure about something, you're visiting the wrong stores.