everything electric is disabled

I just tried to start my Passport this morning and I got no response at all. When I turn the key there is no sound at all. The dash clock is dead, the lights are dead, the power locks are dead. As far as I can tell everything is dead. Could i simply be in need of a new battery or do you think it is something more involved?

the power was on when I got in the car; the clock was working, and all the doors unlocked, it's just when I turned the key that everything turned off.

I don't have time to try to fix it myself, so I'm debating whether or not I should just try to get a new battery or take it into a mechanic. also, do you think a jump would work, if anything, to at least get it to a mechanic?

I'm trying to get this figured out ASAP because if I don't figure something out before Thursday Thanksgiving will be ruined with no transportation.

Thanks!
-Nick