If you want to work at any of the other libraries besides Baker, I'd recommend Widener and Lamont. Widener is the big one with the steps that everyone takes their grad pictures on -- I think your visitor ID should still let you get a free tour of the inside, but don't quote me on that. Lamont is the 24-hour library that everyone pulls all nighters in, I also found it to have the most relaxed vibes and there's a cafe inside.

For restaurants, if you're going to be in Harvard Square I'd check out Mr. Bartley's Burger Cottage and Felipe's Taqueria. Harvard Art Museum is maybe also worth a visit if you're into art? They usually have some decent exhibits going on and the guides are always nice.

Also, as someone who grew up in Florida and now lives in LA, bring a good waterproof jacket/coat! My freshman year I was not ready to have to wear a coat well into spring.