Each mod is similary as unmodded game a single swf file that you use to play. But when you use mod save will be easy converted from unmodded version to mod but no longer will be possible to return to use such save to play in unmodded version.
As for corruption to make fast reducing it afterward you can visit Arian when he's in camp (he can lower corr slowly), get felp from Jojo or Gargoyle at cathedra to undergone ritual of purification.