Help with wiper motor case isolation

[RiftFlyer]

Hi Guys,

I just picked up a few VW wiper motors (Bosch). I need to run a separate ground line and isolate the motor housing as I am using a metal frame. I find information on this difficult to find. The only tutorial I could find was in French.

I have removed the bell housing. I have three brushes which I assume are ground, high and low speed. It appears only one of the three is connected to the motor housing (near screw in the first picture) so I assume this is what I need to cut, isolate and run my ground wire from. Could you guys take a look at the pictures and let me know if I'm on the right track. I am also unsure if I need to modify anything in the park circuit in the gearbox. Can anyone help with that?

Thanks.
EDITED: Added gallery pics instead of external links.

[RiftFlyer]

I went ahead and cut the grounded brush and soldered a wire in place. I added heat-shrink to insulate the connection and routed the wire out through the existing grommet . I don't have a light tester but I checked each wire with a multimeter against the motor bell and have no continuity. I think I am good to go.