You don't have to! HyperCard periodically saves changes you make.
Use the Finder to copy any stacks you're going to edit. That way, you'll be able to go back to a previous version of the stack. (Use the Open Stack command.)
You can have stacks with the same name, as long as they're in separate folders. HyperCard always tries to find a stack it needs by looking first in the folder the current stack is in.