Well, I'm sure Tanya can get information about places to see (museums, churches, red square) in a visitor's guide. It's perfectly normal to wonder if there are any special restaurants that she should experience as well.
Anyway, I haven't been there in over 7 years so I definitely wouldn't know what to recommend. But I do know that you can get a very nice deal if you stay in an apartment instead of hotel. A deal not just financially but location-wise. My cousin went to Moscow for a few weeks this year and the year before. Both times she "registered" with a hotel for just about $100 but ended up staying in an apartment with a view of Red Square and walking distance to Arbat. And it didn't break the bank either.
Other than that, just prepare to be shocked by prices like Karkusha said. Enjoy your trip!