No, actually what I was trying to was was just install the base version right into your existing Oracle Home, do a custom install and choose to install CMAN only, you won't hurt your existing home. After you install it, go ahead and install the patch set again, it'll only patch the things that need patching. I've done this numerous times for customers with no issues.
Like I said, if the process makes you nervous, set up a test to try it out before doing it on your production Oracle home.