Old School SCASM Coder needs help with vectors

I am in the process of making static aircraft libraries for use in FS and for some of the sources I need to re-engineer the code to add some parts (winglets) or change others (Lengthen fuselage of modify wings)
The one thing I can't get my brain around is the calculations of the vectors for the VecPoints and TexPoly commands.

I understand the concept of calculating the vectors for polygons and normalizing the three vectors to 32767 I just haven't been able to reproduce the values in some to the existing objects.

I have read a number of exchanges between Arno Gerretsen and Luis Sa' but am still confused.

Does someone have a step by step process to walk through the calculations. I use MS Excel for a lot of code modifications so if a spread sheet with notes explaining thins will be great