Couple of questions. How difficult is it to take and pass the Flight Engineer written for an ATP pilot with a few types? Is it similar to the ATP written, or is it completely different.

I know that a written is good for 2 years unless your working for a 121 or 135. What if you have a few months off and then go back to work for a 121 or 135, is it still valid?

Are there any testing mills out there where you can knock it out at, with maybe a limited testing bank?

Thanks