If you stand towards the "back" (closer to Sunset Blvd) and you make a beeline for the F! theater, you MIGHT make it in just before the show starts, but you may be standing to watch it, BECAUSE, your seats will be gone. At some point (I want to say 20 min before show starts), they will open up the reserved seating to anyone who wants it.
So if you really want to do both on the same night, I would not be forking over the extra money for a F! dining package.