you are already familiar with your camera ...
the worst thing is to be unfamiliar with a camera you are
using for a job, it kinda looks unprofessional ...

get the wide lens, the good one for the camera you own now, and
after the job then after you get paid, get the rz ...
just remember that often times KEH ratings are cosmetics, not operation
... i have never had problems but others seem kind of upset ...
( you can search here under KEH to see stories ... so getting a new/used
camera, and then having it konk out while you are using it is pretty bad too )

have fun !
john