No don't waterproof it, it is already waterproof to a 3000mmHH. If it leaks send it straight back.You made the right choice going for the porch, we realised we so need a porch on the Vermont, when it rains you have to have the doors shut or the tent gets wet. It might be raining but still muggy and the door needs to be open. As IAT said earlier, nice to have somewhere dry where you can still keep your mucky footware on.
If you can't set it up at home, what about a friend or relative or book into the nearest campsite to home for one night. That's what we did on one of our first ever camps, we rushed home a bout 6 times for different things, we even fetched a curry from our local Indian. It was just a bit of fun, never meant to be a serious camp and it helped us on our way.
Watch the Montana 6 Video a couple of times until you are both familiar with the best way to pitch it. You would be surprised how hard it is to erect when your not sure of the best way.
and wayne funny enough i was just saying the OH that we should book into a campsite close to us and just for a night away before attempting to go away for half term. Good thinking! 
