Since he just had his first meal, you probably won't have much spot cleaning to do anyway. I'd let him sit on that one for at least a few days. Depending on your bedding and sense of smell, you might be able to know with a good whiff. If you're using newspaper or paper towels, poop is pretty easy to smell. Pee will soak into a larger area and be pretty easy to recognize too, even if he does it in the hide. You might want to get into more of a routine before you try to convert to rats. Let that first milestone set in a bit before you try for the next.