The needle pulls straight off, but it is on the world's smallest shaft and requires care. A fair amount of force is required and be very parallel to the shaft with that force. I use a "cotton forceps" (dental instrument). Mark the spot that the resting needle hovers over (will need to bend needle itself upwards, past the limit set pegs) so that you can set it back to same spot. Re insert over shaft with little force as you'll be recalibrating by repositioning needle several times (off and on, off and on..good enough). I can make any oil gauge read 3 bar at idle, any temp. gauge read 80 (in the Sahara at noon), any tank be full when empty, just by mispositioning the needle.
I switched out a set of gasoline engine gauges to my 300SD and by resetting the needle (and a little fiddling), now use the economy gauge(which is vacuum) as a boost gauge for the turbo(read left to right instead of rt. to lft.). Unfortunately, according to my fuel gauge, I'm getting 400 mpg for the first quarter tank.