Thanks for all your help, I got it done wheew.

I basically broke the old lambda tower to pieces with the center punch and the hammer so that only the two screws where sticking out.

Then I screw those out with pliers. Now screwing the two screws back in with the new lambda tower in place was more tricky, as you said there is no room for pliers or a wrench to grab those suckers and twist them.

I stuck a screwdriver between the screw and the lambda tower "wall" (sideways) and twisted the screws in that way, worked like a charm.

O \ (
^^^ lambda tower wall
^^screw driver using the tower wall as levage and pushing the screw and and twisting it
^screw head