Rockbox'ing an ipod is completely safe. Obviously, the people behind rockbox can't give some kind of warranty, but if all you're going to do is use the rockbox-provided ipodpatcher to install the rockbox loader, virtually nothing can go wrong that can't be easily fixed by doing the process again [correctly] or restoring the apple firmware to its original state. As you probably know, installing rockbox doesn't remove the apple firmware at all.
Dad, as long as you didn't raise a complete retard, it's safe.