1. You bargain the %age off of MSRP that you are willing to pay for the car.
2. Not necessarily, because you can backout at any time, if you are not satisfied - you are not obligated to buy the car.
3. Some dealers expect a $500-$1000 deposit (check or credit card - money won't be withdrawn); others will just take your word for it. In the case of pre-ordering an R-Class, they are just selecting options (on your behalf) for one of many cars that will be delivered in the next few months. They prefer to order cars that sell well, with the right options - your choice happens to be one of them. At the same time, they don't want uncommitted buyers.
4. Yes, it is fully refundable. In fact the paperwork (if you pay a deposit) will say that neither parties (car buyer, dealer) is obligated to buy/sell the car. Its just that you get to pick first, once it arrives in the showroom.
5. I read in another web site that the new colors on the 2008 R-Class are calcite white, sanidine beige or periclase green. Your dealer should be able to give you specifics when pre-ordering the car through the online system.
6. I would buy, because good (discounted) residuals and Money Factors exist typically for 10k, 12k and 15k/year leases only. If you get a very good pre-purchase option for the extra miles and are able to negotiate, then it might be worth - but I have my doubts. And I know that some folks lease for business accounting reasons.
7. Not really. Lease companies expect you to have good insurance coverage for liability - which considering the car you are able to afford, would cover the minimal 100/300 (or whatever) the requirement is.
8. The car is built in one of the most sophisticated auto assembly plants in the world (Check out
http://www.mbusi.com/). That said, there is some pseudo-prestige / hype (and surely some historical evidence) that cars built in Japan and Germany by their original manufacturers are better (or truer to their heritage - as applicable). But keep in mind that newer plants are designed better to produce new models, using the latest technologies, resulting in more automation and stricter QA/monitoring. The R-class is not a collectors car, so I wouldn't bother too much on this point.
And just a fyi - I ordered my 2008 R350 a couple of weeks ago.