Navy Vet considering a MM career

Hello - I’m a Navy veteran and I’ve thought about becoming a Merchant Marine, but I’m honestly not quite sure where to start or what the process looks like.

I’m hoping to hear from people who are currently working in this industry, especially anyone who came from a military background.

A few things I’m curious about:

How does my Navy experience/credentials translate over, if at all? I was an ABE (Catapults)

Are there union and non-union routes?

What does the career progression typically look like?

What kind of pay and benefits can someone realistically expect as they progress?

What is the lifestyle and rotation like?

Is there anything you wish you had known before getting started?

I’m not looking for someone to sell me on the career—I’d really appreciate the honest version, including the downsides, challenges, and things that might surprise someone coming from the Navy.

Thank you in advance.