That's an interesting route, I would love to visit those parts of Europe.
It's kind of pricy over there. From road tolls to hotels to bottled water.
I don't think there is a need to book hotels in advance unless you are aiming for down-town luxury ones. There is a neat iPhone application called Hostel Hero
trough witch you can browse and book all sorts of accommodations from 5e a night to five star hotels. That part of the world is very much industrialized and civilized so you shouldn't worry so much about food, accommodation, medical help, fuel etc.
That also brings me to tools - Versys is a healthy machine when treated properly. Fuel and oil is almost all you need for 5-8000km. It comes with some (flaky) tools under the seat witch will do well in an emergency. You could carry a can of chain-lube but you can buy a can of WD40 for 3-4e in any gas station along the way. I do carry some basic tools wherever I go for peace of mind, rarely use them though.
Crash bars - I wouldn't say it's a must but it's another peace of mind. Available from Hepco & Becker and SW-Motech. Either will set you back around 150e.
Skid-plate on asphalt roads? Overkill. I did it so I know. Not many available for the Versys but that may change in near future. Mounting it on this bike is a bit tricky so they are more engine and exhaust shield then a proper skid-plate.
15e front fender extender will shield this part from mud and water being trown by front wheel.
A lot of luggage options for the bike. I don't subscribe to hard side bags so I can't tell you much about those but there are mountains of info on the forum. A nice GIVI set can cost up to 500-600e. (not sure about Moscow prices, I know that bikes are crazy expensive over there
Hope this helps a little.