If the rate is anything like that of computers or other complex technical gear, they will need plenty of engineers. Nowhere near the number of people they are replacing on the production lines, but still not an insignificant number.
I doubt that. You need humans to construct and program robots. There is no reason why you'd need humans to maintain and repair robots.
For a (slightly contrived) analogy you could look at modern farming or datacenters. It's not uncommon for a modern farm with thousands of cattle to be run by a work force smaller than 30 people. The same is true for datacenters that house ten thousands units of rather complex machinery.
In purely manual labor (assembly lines) a 1000:1 workforce-reduction doesn't seem unlikely.
