I took the RS tour and when it was over took a river cruise which ended in Moscow. I would check seriously into the visa aspect because I think you need a visa whether or not you are there for less than three days (in most circumstances.) There is an exception but it (to the best of my recollection) had to do with coming in and going out and doing only things with escorted tour groups in a "Cruise Ship." You enter Russia via train on the RS cruise and I am fairly certain everyone on the tour had a visa, even those not staying on when the tour was over. This is what I found in Wiki about it:
Visa-free visits for up to 72 hours for cruise ship and ferry passengers
Since May 2009 international tourists entering by regular ferry via
several ports have been able to stay in Russia visa-free for up to 72
hours, provided that they spend the night on-board or in accommodation
specifically approved by the travel agency.[6]
In addition tourists entering by tourist cruise ships can leave the
ship visa-free on tours organized by any authorized local tour
company, when entering Russia through the ports of Anadyr,
Kaliningrad, Korsakov, Novorossiysk (Port of Novorossiysk), Murmansk
(Port of Murmansk), Sevastopol (Port of Sevastopol), Sochi (Port of
Sochi), St.Petersburg (Big port Saint Petersburg, Passenger Port of
St. Petersburg), Vladivostok, Vyborg, Zarubino (Port of
Zarubino).[7][8][9]
Entry to the port of St. Petersburg by regular ferry can be done only
from the ports of Tallinn (Estonia) or Helsinki (Finland). It is also
possible to travel visa-free for 72 hours from the port of Stockholm
with the stop in Helsinki.[10][11]
Although I would love to return to St. Petersburg, I am okay not seeing Moscow again (however I would go back if circumstances warranted, it was an interesting place.) In my experience, fewer Russians speak English than in many other parts of the "urbanized world" and it would not be the easiest country to try in on your own. I've taken many trips on my own but would likely not enjoy Russia nearly as much as I did without a good guide. I would not be too worried about the political situation. If you are, take trip insurance and, as stated above, it is likely RS will try and protect you if they think anything untoward is happening in the region. Personally, if I didn't have other places to see right now, I'd go back in a heartbeat.