I have never installed a Mod on any video game. I have been tempted to install player created quests for Neverwinter nights, however I'm a Scaredy Cat as I am ignorant in the ways of code and techy things, I'm afraid to catch a virus or something or another
NWN modules are pretty safe, they are essentially fanmade expansions/DLCs. The actual mods in the classic sense are the .hak files, that contain new models, textures, 2da files, etc.
If you're still interested in NWN, there are several incredibly well-made modules for it.