Yeah it is almost as simple as that, BUT the init.rc is stored in the boot partition, and the galaxo one loads some extra/other stuff. So if u update with the galaxo kernel it may not work properly.
I would suggest you compare the two init.rc files and see if it looks workable. Or make your own boot.img using the original init.rc and modifying the mounts (we use no atime to speed up the system)
You could also ask drakaz to build u a stock kernel update. Thats what i've been using since we created this custom kernel