Your loan officer should be able to change the down payment and loan price for you.
It may require updated forms if you loan is a FHA loan but hey who care underwriting dhould only take 2-3 days at most so you would still have plenty of time to close. My only concern is why would you want to put an additional 5000.00 down on a home at this time it will have a very minimal effect on your payment and with the declining prices may just evaporate in you homes value. I think you would be better off keeping the 5000 as a reserve against future expenses that may arise.
Good Luck, Todd Norsted