Wow. I guess it all depends on your vision and the overall expectations for your project. I would like say something encouraging here but in all honesty, I can't imagine doing a competition worthy Gingerbread project in one day. In fact, I usually budget two or even three months for these types of projects because it can be really labor intensive and time consuming; even someone who loves doing this type of work (like I do) can get worn down after a few hours and I find that forcing myself to move forward will result in mistakes and/or sub-par results. Plus, there are technical constraints (such as the time it takes for royal icing to set up and the time it takes for gum paste to harden etc..) that would make attempting a project in a day a very difficult task.
Again, I'm sorry I can't offer more encouraging advice but I suppose if I had only a day to complete my whole project I would scale things back significantly and go for something very simple like a simple four wall, one roof structure and keep the detail down to a minimum. Most importantly, please keep in mind that these projects are supposed to be fun and don't beat yourself up too much. As they say in all competitions, "there is always next year" and if nothing else, you can plan more effectively next year and create that 'killer entry' then. Have fun and good luck!
Regards,
-Adam