help...wanting to become a cna

today i checked on my application at the lingenfelter center in kingman arizona and the front desk lady asked if i wanted to become a cna because they only had kitchen and i dont want to work in kitchen or fast food:nuke:. i agreed so she put my position applying for as cna. my cousin works there and takes classes he says he has to clean up alot of feces and vomit...i understand that is true but what besides that does a cna do...if i get a interview i want to know what kind of questions they ask so i will be somewhat prepared. if i get the job i will be working with elderlies with alheizmers. i think this job would be good for me because i do want to work in a medical field of some sort....also what should i say for why i would want to work there for every interview my mind goes blank and i cant think of anything to say except to support my family. sorry this post is so long...any help would be greatly appreciated thanks and god bless