ferets, like every member of the weaselfamily, have scent glands near the anus. They only use these when scared, to scare of atackers. Even dogs and cats have these glands. These glands are removed with descenting. The danger with descenting is, that they are almost on the anus, while removing the glands sometimes the anus get damaged, makking it unable for the animal to keep poo in his body.
The strong smell (musc) ferets and skunks give normally, is only produced during matting season by the malles. With neutering your ferret you wont have this smell.
It is always better to neuter your ferets. If the female's get in heat and don't mate, they stay in heat. This will cause problems with the white bloodcells and the female will eventually die. (It is a lot more complicated, but i can't explain it english) The male get very agresive during season to other ferets (and sometimes even to owners) and they smell awfull. I normally wait till my ferets reach maturity untill i neuter them.