OP is a technic guide. Flashing ROM is up to you if you want KitKat install and see what happens.Because you can always re-install stock firmware with Odin software. A lot of AOSP ROMs has Samsung's signature you don't have to root your phone (or install a custom kernel) BUT
if you edit the zip the signature will be broken or if you just want to make sure do these;
Now for installing you don't have to install kernel. You should root
and install temporary recovery
with stock recovery. Then you can do whatever you wantbut CWM is temporary you should re-flash everytime if you don't want to install custom kernel otherwise with custom kernels you will have permanent recovery.