Ideal replacement on the wife's 2009 ML320 Bluetec. Pulling the old blower out hardest part was taking the wire clip off the by the passenger foot light and fuse box on the plastic bottom trim piece. After figuring out to pull the hard to see locking tabs at the ends out it came right out. Installation the same wire clip took some time. Putting the bottom cover back on... I found it was best to put the foot heater vent up inside, take the storage netting off on the left leg side. Install the bottom trim piece (easier said than done) try and get the dividend vent under the back clips on the cover. Push pull sideways trying to get the front of the vent under the clips. I kicked out and the wide side of the vent went right under the clip. The left vent I used a small screwdriver to get the tap over the foot, then pushed and pulled the vents sideways and it finally popped in.
Not a lot of room to work the cover in. Put some kind of cushion over the bottom of the door opening. I'd say have fun, but you probably won't. Yet I'd do it again over taking it to a shop....