No experience, but some info that might help.

Instructions for Sedan & Wagon, as per eBahn manual: (Images were not copied/pasted here)

Roof Antenna Removing:

Sedan:

• Remove roof end strip and both C-pillar trim: Body Interior - Repair Group 70
• Remove both rear grab handles under roof
• Carefully lower molded headliner slightly in rear area
• Remove nut - 2 -
• Disengage harness connectors in antenna wires, disconnect them and remove antenna

Wagon:

• Remove roof end strip and both D-pillar trim Body Interior - Repair Group 70
• Carefully lower molded headliner slightly in rear area
• Remove nut - arrow -
• Loosen connectors - A and B - at plastic bracket
• Disengage harness connectors in antenna wires, disconnect them and remove antenna

Installing:

Install in reverse order of removal.

Note:

When inserting antenna, ensure gasket is properly seated.
Both guide protrusions of gasket must be seated in the appropriate holes - arrows - in
antenna base.
When inserting antenna, make sure antenna wires - 1 - are routed correctly through the
wire pass-through in mounting nut - 2 - .