I have been to Russia ten times in the past year, it will be no problem; although I would advise you get a one year business visa with multiple entry. I used to do single visas for Russia entry but that gets expensive very fast.
Business visa is not hard to get, only need an AIDS test (HIV), letter from Russian business, etc and a little time to get the visa. Like I said, I have been 10 times in past year with no problems. They even know my by face I have been though Moscow so many times; the waiters at TGIF restaurant know me by name.
No worries mate; go and see her; this is your life together.
