Is there some reason to believe you couldn't simply get cash out of an ATM upon arrival? Mainly a question about the airport and perhaps the Russian ATM networks in general...

Only "gotcha" I've run into personally is that some international ATMs automatically pull money from your checking account. So if you're someone who traditionally leaves $1 in checking and your actual balance in a shares account, you may need to move your ATM cash over into checking before you go.