Russia is fine. Just try and stick to the rules, be humble to anyone in an official looking hat.
Its similar to Morocco re the bike - You buy insurance at the border, just take your licence and registration with you. You will get a customs form for the bike at the border. You will need to get a visa before you get there. Its a bit of a process but I get my invitations from
www.visalink.ru, then you send your invitation plus visa application, plus money away to get processed (I tend to use the Edinburgh consulate as it is faster than the one in London).
Legal alcohol limit is ZERO, so do be careful with that. The only option to going to a russian prison if you have even one beer and get caught is buying a special limited edition ticket to the policeman's ball, currently running at about US$1500 around Moscow (might be a little cheaper in the boonies)
The last few years has seen a huge bike boom in Moscow, and Friday night and Sat night have all sorts of bike gatherings. The local bikers will take to you like a brother. Try the main street (Tverskaya) at midnight or out in front of the main University building at MGU.
Have a talk to Tony P on the HUBB ... you should be able to find plenty of his posts on
http://www.horizonsunlimited.com/hubb/northern-asia/ ... He is in Uxbridge half the time and Moscow the other half and sometimes rides an F650 between the two.
Fuel is generally about half the price of here. Moscow is expensive (or very expensive) for everying else. Road atlases are pretty abundant and inexpensive these days especially for european Russia. I would advise at least one person in your group to try and learn some basic Russian. And all of you should learn the Russian alphabet. Its only 31 letters, and many of them are the same as our alphabet anyway. It will make a HUGE difference and you should be able to learn it completely in a day if you are serious.
By October, you wont have a lot of time before its too cold ... It may already be flirting with pre winter light snows in October in Moscow ... or it may be 15 degrees.
Also the Russians ... they are great people but typically have a cold gruff exterior. The shell is pretty thin ... if you give them half a reason to like you, then you will drown in hospitality. Do not be put off by gruff exteriors cause they really are only skin deep.
Finally have a read of Adrian Scotts book, The Road Gets Better from Here (PM me for details) and the Mondo Enduro diaries.