Youra,
I'm in the middle of completing rearranging my workshop, and have been unable to physically get to the drill to have a look, today after a lot of junk was thrown out I managed to make some space.
I've taken a few photos which should help hopefully.
Firstly loosen the 2 grub screws at the rear to slacken the belt, all screws are imperial.
Unclip the return spring, then unscrew the cap head allen screw from the underside holding the pivot arm in place.
Unscrew the single cap head screw on the front holding the spindle in place, you might need to twist apart lightly with a flat head screwdriver, mine pulled out relatively easily.
There's 3 screws on the bottom of the spindle holding the plate on, I photographed this, you can see the bearing inside, I can't find the little chuck key, and have a drill in the chuck, so couldn't see if the chuck had a screw, I wouldn't have thought so, probably just a press fit.
The top of the spindle needs a 2 pin castle type socket to get the upper pulley off, the pivot arm has a pin that needs pressing out
So once you have the spindle off the drill, take the pivot arm off, pretty simple, take the chuck off, make a suitable socket for the upper pulley, and it's just the bearings in the sleeve, all very simple.