Does Spanish as spoken in Mexico differ from Spanish spoken in Spain in terms of grammar, or is it just vocabulary?

Answer 1

It differs just like American English and British English do. The grammar is the same and you won´t have a problem being understood in either country. Some countries use another pronoun, vos, instead of tú and others use usted and don´t use tú at all, but you will be fine traveling and communicating in any of these countries, in my personal experience. I hope that helps.