I have a FW I'm working on right now that smells really bad too. The case smells like an active mouse nest and the machine has the rancid oil smell.
I can deal with the machine smell by making a new felt drip pad for the bottom cover. As for the case, well that might take some doing.
We used a bag of ceder shavings, amongst other things, to help remove the most of the odor from ours. But it wasn't as bad as this one.
I'd use sewing machine oil and a soft cloth or a make up removing pad to clean the surface. It might not happen on your machine but I've had water and soap turn the clear coating on black Singers milky white.
Joe