International Assignment from U.S. to Russia (St. Petersburg)

Good day!

My name is Ernesto and I currently reside on the United States. I am originally from Mexico and I am residing in Austin , TX. I'm finishing my graduate studies in may Protected content I've been thinking about taking an International assignment my company is offering for next year to St. Petersburg.

If I get the position, the assignment in Russia will last 3 years. My company has not given me any training yet or whatsoever since the position is not mine yet. I decided to take initiative and start getting some information about the country and advice from people from the United States (or Mexico) that live there.

I have a couple of questions:

I know the people from my company there will speak English but outside work , my lack of language and communication skills in Russian really worry me. How hard is to learn the language and how different is the culture from the U.S.? (what I mean is, how do they relate to people from outside the country, or how close and openly do they speak/relate)

On compensation, my company offers two different kinds of packages: the balance sheet and the local plus. Which one would be more beneficial?

I appreciate any type of advice

thanks in advance.