Belorusskaya Metro and train station are at the same place, near where Tverskaya turns into Leningradsky Prospekt.

It's a 30 minute walk all the way down to Red Square, but If I'm not mistaken the Marriot is quite close.

Getting there will be a challenge, I understand things have gotten more difficult over the last few years. Going to the Novotel in front of the SVO I terminal might help, I was once allowed on the shuttle downtown many years ago mind you, but taxis might be a little easier from there.

Do you know anyone there who can hire a driver to meet you?