Hi pm,
I am also a newcomer in the modding world, but I finally did a nice (in my opinion) new map of Spain (and Portugal, of course) for the Reconquista Mod.
It is true that there are some problems with the script generation. I did it easily the first time, but in the two modifications of the original map the script cannot be generated because some error with the bifpalette or something like that. (PLEASE, HELP REQUIRED IN THIS POINT)
Sometimes my campaign did not appear in the menu. One crucial point in VI is to put at the end of each line in SetAttributes the parameter TRUE for the victory conditions. This word does not appear in the script from LMM (not necessary for MTW 1.1) but it appears in the scripts of VI.
It is necessary to create new folders (duplicate and rename the existing ones) with the name of your mod (you can find the list in the repository).
The next problem I had was the "error loading offscreen" message, which can be solved by correctly renaming the LBM files generated by LMM.
Thus the campaign was loaded but it crashed to desktop. A crucial point to prevent this (I discovered last night) is to build a new region_specific file for your mod, because all the data of the new provinces MUST FIT with the data in the script of the startpos folder. I am not sure if it is also necessary to complete other files such as names and descriptions, but I have done it just in case.
In any case, I am not an expert and I am stacked in the crash to desktop problem after the first turn.
GOOD LUCK (we need it).
I will try to share my progress.