The Late Night Expansion...

I'm sorry, this isn't exactly a problem, it's more of me trying to avoid uninstalling and reinstalling everything. 
I was wondering why late night had all of the extra instructions and steps and all and if I could avoid them. 

I currently have all of the expansions except Late night and Worlds and some of the SP's.

Hi there, @Puke!

Are you talking about the Installation Guide that comes with the game torrent? If you downloaded Late Night on it's own (and not the Complete Collection), then the guide inside is outdated. This is what you should be following:
https://games4theworld.forumotion.com/t1171-must-read-how-to-install-the-sims-3-correctly

So, just make sure that your game is updated by applying the Manual Patch. Then, install the expansion pack just double clicking the Setup inside. And finally, apply the Ultimate Fix as the Steps 4 and 5 of the guide above say. You shouldn't have any problems then.

Please, let us know how it goes. Good luck!