To remove the sensor just cut the wire and use a socket. It'll come out easy once you manage to get into position. Spray a little silicone on the grommet to slip it into place (keep away from O2 sensor). The sensor does not have to be tighted too much. There are no "forces" trying to pop it out. If you put too much torque on it the end might snap off... and THAT IS a real PITA.
Good luck ,and yes, it would be a lot easier if the damn shock wasn't in the way
