mbenz: g-man is right, i guess I should have made it more clear in my posting as well. You HAVE to use an RI, they have to do the mods - if they don't do the mods, they will charge for them anyway.
Here's the deal - I spoke to three RI's about this as well. They all told me the same thing:
When they import the car, they act as the manufacturer i.e. they assume liability for recalls, damages which are caused by the car not being to US standard, etc, NOT Mercedes. Therefore, they are not going to take the chance that you did the work properly. The RI's I spoke to told me I would be looking at 1-2 months of the car sitting in customs, being modded, or being inspected before I would see it as a minimum.
Check out http://www.nhtsa.dot.gov/cars/rules/import/newsletters/
to get an idea of the rules (and penalties) these guys face.
another thing to be concerned with is when you get the car here trying to get it insured. A lot of insurers won't touch grey market cars for the same reasons listed above.
I think the bottom line here is the hassle and expense you will go through to get it here, not to mention the grey market spectre which will loom over the car, will make this car a break even proposition at best. You might make a paper profit, but unless you enjoy headaches, heartburn and waiting, it will be a bust. The US government in cahoots with car manufacturers have made this a difficult proposition.