Newest version - Do I need that data file?

I won't be using the iron launcher. Will I need to replace my data folder with the file in the FAQ thread for this latest version?

You might need to yea.  But remember to KEEP your old data file under the name NativeData.  You will need it when you go to play other mods.  Of course all the berserk data is in the data file in the Revenge of the Berserk folder.  You could simply copy that over to your main Mount&Blade folder.