I also had to get some Tomall adapter clips to put them in (these clips were awful). It took a bunch of bending and modifying to make this clips work and they still don't work well. I later replaced them with a set from Lasfit directly which were somewhat less bad. I ended up taking the retainer from the bulb and welding it to these adapter clips to hold the 2 pieces together so I could install them, and then insert the bulb.
The E350 uses H7 bulbs. They are unpleasant to work with as they have these metal retainers that cut you to ribbons when you work with them. The factory integrates this retainer into the connector making it easier. The passengers side is easy to access but the drivers side is very tight. I am able to get my hand in there somehow but its hard to work with the retainer. To make it easier, I welded the retainer to the collar that comes with the Lasfit bulbs, installed the retainer clip and collar assembly, then pushed the bulb into place.
I had my passenger side headlight burn out so I changed it first. It was cold so I did not spend the time to change the drivers side at that time. This gave the opportunity to compare them though. A week or so later I finally changed the drivers side too. The videos below were shot with an inexpensive Yi Compact Dash Camera.
Here is a video of the old headlights.
Here is a video with a mix of headlights. At this point I had upgraded the passengers side (right) to Lasfit LED but the drivers side was still halogen.
Finally, both headlights upgraded to Lasfit LED.