To the first question:-
Using a compatible USB flash drive would be the easiest way assuming a). you have a Xbox compatible flash drive and
. you have a Xbox controller port to USB (F) adapter or alternative. You'll need tp install Xplorer360 as well to be able to get at files on the drive as they'll be in FATX format.
A standard memory card can do the same thing but you'll need a Xbox controller to PC USB(M) adapter and Xplorer360 for this as well of course.
If you've got an official memory card I'd go for the second method simply because finding a Xbox controller to USB adapter is easier than finding a compatible USB flash drive.