Hi Janey,
I don't have an Atlas machine(yet!) so I'm probably not going to be much help but I've got a few thoughts.
I haven't seen a manual for this particular machine, but right now I'm working on the Wizard machine I got from Margaret and it's almost identical to yours except it doesn't take cams (model 3KC-8846). So you may have to expand your search to include other Brother built brands(go by picture not model), and close may be as close as you can get.
From the cam you have, and this is just a guess if I remember right, the Atlas machines had a little bigger cams than most of the Brother cams I've seen or have. There is a brown set of Brother cams that are a little bigger than the usual black cam sets but I don't know if they would work in your machine. I've only seen pics of a set of Atlas cams once and can't remember what they looked like, only that they were in a marked box. Do a google search of Atlas machines and see if a pic comes up showing a machine with its cams.
The wick thingy is similar to what some of my Brother machines have. If the wicks are hard then you should clean or replace them. Is there also a plastic oiling system, or what I call an oil rail on the under side of the machine top? My machines that have this wick also have the oil rail.
Cari