Congrats! You will like the car, it can be a long term relationship if you get a good one. I have had one (2 door gas powered) over 10 years.
There is some information about options here:
www.mbcoupes.com
The buyer's guide section is where you need to look, it has maintenance tips too. Never hurts to get up to speed on those
You might even want to buy on ebay the S Class sales brochure for your year, it will have information and pictures you will enjoy.
Get the MB Net (sometimes called Vehicle Master Inquiry) for your car, it will have a list of options on your car, date of build, first sale, name of dealer where it was sold, description of warranty claims and more, but you will need to prove ownership of the car, and get a co operative parts or service guy to decode all the "DCOMP" codes on it, as the damage codes are all numbers.
There is also a Russian MB site (someone else here will know the link) you can run for your car, it is free, just punch in the VIN
Call 1-800FORMERCEDES and ask for your free photocopy of your car's original window sticker.....(if this is your first Benz, you should know you can call this number if your car has a dead battery flat tire or runs out of gas, and they will send a service vehicle out for free, dealer vehicle or contracted tow truck in rural area, available to ALL Mercedes owners, no matter how old the car, never a charge)
Also, you can get information in depth by writing to the Daimler Chrysler Historical archives in Stuttgart (Respectful letter with copy of proof of ownership of the car) and ask for a copy of the car's build sheet (in English of course) and in a month or so, you should get it (it is free)
It is a long shot for a car as old as an SDL, but you could
maybe look in the maintenance booklet, and call the shops who stamped it, they might remember the car and tell you about it, and if you are lucky, get copies of the records. If requested by mail, a $20 bill for "Photocopies expense
" will probably help a lot. (This worked VERY well for me!)
Use the Diesel Discussion section for tech issues and questions, and try also the W126 section of
www.benzworld.com - there a LOT of friendly people ready to help you, quick.