My last pond was not escape proof and several of my turtles escaped never to be seen again. This is why I've been harping on that point so much. Anyway, one turtle did return after nearly a month out of the pond. There was no other bodies of water around for miles, so I can only assume that he spent the entire time out of the water. After returning from his little "walk about" he was a little dried out and his shell had a few dings and scratches on it, but he seemed healthy and was certainly full of energy. He also seemed happy to be back in the pond and resumed taking food from our hands the very next day.
As Haro and Ruben stated, a few hours out of the water would do absolutely no harm.
But Ruben has a good point about not letting them get knocked around. For instance, you wouldn't want to put them in a large container with just enough water for them to float around in, because as you drive the water would be sloshing around and so would the turtle(s), that would be a stressful trip for them. A dark sealed container with a damp rag on the bottom would be ideal, as it would help stop them from sliding around and keep them calm.
I'm assuming if you get them now you'd be keeping them indoors, and won't be introducing them into your pond till the spring, right?