As for the dm file, it depends on what you modded, a few fixes are needed (e.g resource costs), but you also have to implement a few new sections (e.g. now you have to specify the type of forts)
I have made so many mistakes in my old mods it feels like I'm doing new mods instead of fixing the old ones.
There are a few new commands for the nation section, some of the old monster and weapon numbers has been changed, armor names has been changed.