let's look at the schedule...
since you're in wave 1 let's assume a sub-3:30 marathon - you should be able to do that even if you have a crappy day or it's really f'n hot (which can happen)
10:00 a.m. race start
1:30 p.m. cross finish line
so you have roughly two hours to get out of the finish area, change clothes, and to the airport. it will take you anywhere from 5 to 15 minutes to get out of the finish area.
IMO you will need ether:
1) a hotel reasonably close to the finish area and a T stop or
2) someplace to store your luggage and change after the race that is reasonably close to the finish area and a T stop
figure out your logistics in advance. have a T pass already in hand.
decide whether you will drop clothes at the BAA bag drop area so you can pick them up after the race (with a hotel close enough to walk to, this won't be necessary) will be more important if it's really cold (which it can be) or if you have a ways to go to get back to your hotel.
i would not rely on the blanket/poncho they give out to keep you warm/dry/comfortable
but like others said above, why bother to be in such a hurry?
you're saving hundreds by not paying for a hotel on Monday night... spend the $$ and give yourself time to recover, hydrate, get some food, walk around a bit, etc... before getting on a plane