I have been to Russia (within the last four years) and I'd advise you to use a good U.S. travel agent, simply because the Russians don't have many mid-range facilities and you'll want to make sure you don't get stuck somewhere.
(The first night we spent in St. Petersburg, the wall in our hotel room caught fire! Try telling a desk clerk who doesn't speak English that your wall's ablaze as you stand in the lobby in your bare feet & a sleep shirt!)
Unless you speak/read Russian, having a local guide is a very good idea....ours was indespensible. She insisted we do some things which turned out to be great ideas we'd never have chosen.
St. Petersburg is a GLORIOUS city with amazing things to see. You'll want to go to the Summer Palace and see the cathedrals and take a boat ride on the canal, because the city was designed to be seen that way. The museums are fascinating. In retrospect, I wish we'd done some research ahead of time on the tsars, but we did manage to pick up some facts along the way. It's interesting that they don't want to discuss the Stalin era, but you find TSAR-related information and souveniers everywhere. You can buy those "matrushka" dolls with tsars, tsarinas & royal kids on just about any corner where tourists are.
We took a river cruise on the Volga from St. Petersburg which was great fun because you see the countryside, some villages along the way and we all fell in love with the Russian crew on the ship.
Moscow is another story....and although it was fascinating to see the "touristy" sites, parts of it were downright eerie and I'm very glad I wasn't alone. I'm not a fearful traveler, but big cities are just about all the same and there's considerable poverty there. Interestingly, people in Moscow are often walking along the sidewalks drinking vodka at all hours of the day/night.
Going into the Kremlin, with all its history, was sobering, especially if you grew up seeing all those May Day parades! Again, I think it'd be VERY difficult to get around without some sort of guide. Reading the Russian alphabet isn't easy and it took us a couple of weeks to begin to recognize signs and menu words.
Oh--speaking of food. Take granola bars, peanuts and anything else you can stuff into luggage. The food was really bad. Unless you like overcooked vegetables, herring, caviar and beets.
I'm very glad I went and will be happy to share more details if you want to message me.