It seems you've confused a couple things, I'll clarify.
On these phones, CWM is included with the custom Kernels provided by Entropy512, or Ktoon or Siyah, et al. CWM however, is not a Kernel, when you boot into CWM mode, your bypassing the loading of the Kernel. Think of it like this. When you press the power button (and only the power button) on your phone, it's hard wired into the phone to boot the Kernel, the Kernel sets up a hardware environment, loads the RAMDisk etc and does it's thing. IF you have a Kernel that includes CWM, you can bypass this by loading CWM INSTEAD of the Kernel. Note, you need to reboot into CWM or use a different set of buttons to get there, power alone, is hard wired to boot the Kernel.
If you came from a different manufacturer, say Motorola, the above process is different, as they lock their bootloaders and you cannot change the Kernel, you use a different process to load CWM, and boot to it instead of the Kernel. As Samsung has an unlocked bootloader, the process of getting CWM is much simpler.
And Mattdm is 100% correct, no need to flash your stock recovery, it's easy enough to download it. If you've got your phone all setup just the way you want it and want to make a backup of it, boot into CWM, scroll to backup and restore, press power, choose backup, use volume up/down to scroll to backup and press power. It will create a backup in a folder called Clockworkmod. It can easily be restored via CWM if you have the need too.
Hope this helped a lil.
Wink
