How do I start to program a 5 axis part with a Trunnion on a Mazak 430B using Mastercam 2021

This is a disaster or this is a great opportunity. I hope it's the latter.

Our two senior programmers quit to work elsewhere. I have only programmed 3 axis VMC. My...boisterous boss says he wants this done and "what have you learned all these years if you can't program this".
While there are several reasons that is not at all fair I will not go into them.

Could anyone of you please be so kind as to help me get started with program. If I could get a model of a similar part programmed with mastercam 2019 or later to follow. My biggest worry is how to start.
I have the solid of the table, trunnion, vise and fixture as well as the solid model of the part to program.

I have heard you must find the table to trunnion centerline first. Then find your stack up which is your vise+fixture+part. But after that how do I approach it in mastercam? Where do I set my work coordinate?
at the top of the part or at the center of the trunnion. Then how do I go about toolpathing it in mastercam.
Boy I think I am screwed.
Please Please someone help me?