I've been watching and posting in your search from the very beginning.
I'm sure you're going to love this car. The W126 is considered to be one of the best cars MB ever built, and the 3.0 liter SOHC inline 6 is a well-regarded, reliable engine that has a history of longevity and durability.
Take my advice - review all of your records to see when the last maintenance was performed on all of the fluids and filters.
The manual will tell you to change the oil and filter every 7,500 miles (which seems waaaay too long), and change the plugs, filters, and transmission fluid every 30,000 miles.
Basically, all of the maintenance is carried out in miles, except two items, which are done on time - brake fluid and coolant replacement. Change your brake fluid every 2 years and coolant every 3 years.
If you have no solid record of any of the above maintenance items, do them now so you can start off with a clear conscience and a clean slate, and then continue with the mileage intervals in the maintenance booklet to keep your maintenance history correct and organized.
Here is a link to the Mercedes Benz homepage. I've keyed it up to the page on your vehicle and you can see how many were sold by year, and how much they cost. You can click on the links for the specs on engine, interior features, etc.