OP, the one crucial fact you left out is whether or not you're going for a MY2009 (in which case you have your pick of the litter in inventory) or a 2010 (factory order).
MY2009? Wait a month and you can probably get it for under 50k. I kid you not. In fact, I'm sure you can probably gun for $48k. After tax, that's.. around $54 flat? You'll be paying a 17.5% luxury tax.
If your mother is Chinese, you may want to bring her to the dealership as well.
My understanding is that MB has a July 31 deadline for selling the previous year, so July 28 onwards should do nicely.
MY2010? Good luck if they give you $100 off. They do NOT bend on factory-ordered cars. Trust me, I tried with 3 dealerships back in 2003.
One guy you may want to try is Raymond at MB Broadway, he sold me my 203, and I was VERY happy with him. PM me if you want more details. I can give you a referral.