On the first point, I haven't played the game, so I don't know the context, but I think it should be either:
"If you don't do what they want by tomorrow, each night of the year will become the longest night of the year."
OR
"If you don't do what they won't do themselves by tomorrow, each night of the year will become the longest night of the year."
On the second point, there are various ways to handle this. For example, see the tin box in 'Seeker of Magic' for the simple approach. This is similar to what you are trying to achieve. (You will see some more sophisticated containers in 'Santa's Trainee Elf' once it's published.) Chris' point was that you should be able to close the trunk and update the graphic. For examples of this, see the various doors in 'The Witch's Apprentice'.