Based on my recent experience, do not replace this sensor unless you have diagnosed that it is definitely not functioning correctly. Although only secured by a single screw to the block, it may be held in the block itself by years of oil, dirt and crud. If that's the case there's nothing to grip or pry on except for the old, brittle electrical connector visible on top. When it breaks off (as mine did), you may find the only practical way to get it out is to drop the clutch and remove the flywheel (as I did), and drift it down and out into the bell housing. A real PITA, but I had a few WYIT's that needed doing anyhow (though I had hoped to do them somewhere in the future).
Glenn

 

Eeyoow!
Is it not possible to extract it by drilling through and pulling upwards...with something?

 

That was my initial thought, so I wasn't too concerned when it broke off. But the magnet proved very difficult to drill. Made virtually no progress with (and broke) a cobalt bit. I think it was suggested I use a small Dremel diamond bit. Might have worked I suppose, but the magnet while being hard, seemed to fracture a bit under stress. I could see myself just getting into more trouble (maybe making the hole out of round). I elected to take what seemed to me the maybe longer, but surer and safer, route. Someone with more skills and experience than me may have been successful at the "drilling and pulling" method. But hey, for some cars it comes out no problem. Better to be lucky I guess.
Glenn