That's a good question Bubba 54. Interesting to learn what you find. Been to St. Petersburg twice in recent years and enjoyed the visits very much. VISA no problem, if you take an escorted excursion that is , either the ship's or one of these more reputable excursion outfits, they take care of the Visa's for you under a group deal, there are three good ones based upon comments on another forum. But you probably know all that, since you are entering by ship and leaving by air, a Visa for Russia is a different story. I like Rick Steves' travel programs, I figure he gives good advice:
Once upon I time I worked for Alaska Airlines. We flew into Khabarovsk (Same latitude as Seattle) in the Far East Federation, once a week from Anchorage. We then took tour groups all the way to Moscow and back to Khabarovsk. In those days there were no difficulties, needed passports and we probably got them group Visas (if they were even required). I don't recall any problem with Soviet authorities ever. The years we ran that tour there wasn't ever a security or safety issue for our passengers. One time one of our group lost his "Playboy" magazine to Customs though. But then, those were the days when it was safe in Russia, 49 years ago, Haw. Good luck.