I have a blown light but cannot figure out how to actually get to the light to replace it - anyone done it before?

Most cheaper new cars include an OWNERS MANUAL which has info on how to do minor maintenance. Check your owners manual.

First, check to see if a fuse is burned out. Usually when a fuse goes a second light or electrical item also does not work. Check your owners manual for fuse box.

For a 2007 you should still be under warranty anyway. Is this an external light? A self contained light or is it part of the car design and you have to access it by going through the back side?

Is this an add-on that you purchased separate from what came with the car? Check the front of it out and see if there are any screws to take out, if so take them out in order, there will probably be a gasket to keep the water out. Remove the bulb, take the bulb to the auto parts store (or pay an arm and leg at a Mercedes dealer) and match the bulb. Insert new bulb and check to see if it works. Check fuse first!

Good luck.