Thanks to pedro66's write-up, I was able to find the parts and get over the stress of drilling into my roof.
Here is the write up. I got tired of my OEM glass mount antenna cutting out constantly so for a while I was using a magnetic antenna. This is a MUCH better looking antenna, no wires seen either.
I didn't get as many pictures pedro's write-up because it was about to rain. I figured if it started pouring I would just cover the hole with tape

As far as the wiring went, I did it slightly different than he did. I cut off the connector that did NOT have the black plastic piece and soldered that to my old antenna lead. Now it just snaps together with the OEM mercedes connectors.
Yes, these are all cell phone pictures, I didn't want to risk dropping my good camera.
Used the same part number he did for the antenna, got it for 11 bucks on
ebay, brand new. Part Number:B6 7 83 0014
The drill bit I used, DO NOT try this with a normal drill bit, you will dent/bend the sheet metal!! The black stuff you see is from my sound deadening.
To be able to reach the underside of the roof, I had to remove both rear grab handles, the 3 round pressure clips in the headliner, and the small bolt that is behind the SRS panel.
The Mercedes connectors
Solder joint to my old antenna cable. I tested signal strength before I drilled the roof, so my connection did not change the signal for the worse.
23" is center from the INSIDE of the black trim on the roof. It is "9.25 from the edge of the tail lamp. If you drill any closer you will hit the headliner support mesh.
The point of no return
Well if you're gonna drill a hole in your roof, drill a big one! This hole is about 20mm like mentioned above.
I did not get a photo of the metal bushing installed, here's what it looks like though. Pull white paper off, mounts on bottom of roof with silver part flush with top of roof.
Installed base part, there is a weather sealing foam under the metal plate.
Plastic cover installed with secondary weather seal on edges
Finally done (except for interior wire routing)
What I finished just in time for