What all do I need to update?

It's probably safe to say most of your mods from two years ago won't work. You could look for updated versions to replace them with, but next week's update is going to break script mods and they'll need to updated again. Since the update is so soon, In your situation I would probably just remove them and play without mods until after the 13th rather than go through the hassle of having to reinstall them twice.

Various types of CC have been breaking from updates over the past two years. You should download Sims 4 Studio and use the tool to run any relevant batch fixes through your packages.

@Cupid Thanks mate.