Hi both
The visa process is a bit long winded and may have changed again since I went last year. I would really recommend using the Russia House checking service as they know all the shortcuts you can get away with in the tediously long form and will happily answer questions on the phone.
As to medicines I didn't go the palaver of getting translations, just make sure you have a copy of any prescription. If you have Bernie as your tour manager you will be in very good hands.
Credit/debit cards are fine in most places including coffee shops tho you may need cash for some entrance fees. How much depends on your spending habits. The vodka museum was a heavy drain on mine!! Being cities, Moscow and St Petersburg are on a similar level to London in terms of cost of items such as drink. For alcohol if you stick to local beer etc then it is slightly cheaper.
Have a great time - it is a fascinating holiday.
Regards
Chris