Merge files or replace them?

[Toosdey]

When the option comes up when installing mods, do you merge files or replace them in MO?

[hishutup]

Well do you want to delete the mod and the reinstall it as a clean mod, select replace.

If you are installing a second part or an update then select merge

[DoubleYou]

If you go to the mo wiki in my signature, there is an explanation in the installing mods section.