I am not an RA, but I am a member of a NPHC org (ZPhiB). One of my LS's was an RA while we were going through our process so I have some experience on the subject. Her job required her to do a hell of a lot of work including planning and attending social functions, forums, dinners with residents, weekly meetings, and even taking care of minor issues such as residents losing toothbrushes in the middle of the night

yeah..i know lol...but u get the picture..While it is definitely a challenge, trust me it CAN be done.
You should be upfront with the people you are going through the process with as well as with the members of the sorority and they should be willing to work with you a little as far as time commitment is concerned. Just make sure you use every bit of free time that you have wisely. Good Luck!