Can i install a mod and use it with a save i already have?

[Luke05]

I wanted to install a charcater customiser mod but i don't know if i can use it with a save file i already have.

[Zane Mordien]

Save a backup and just try out. If it worked great if not then you have the answer and you can just use the backup save. In general most mods can be added anytime with some exceptions.  This may be one of those.