As far as removing the glass cutting wheel you are along the right track with a bradawl or an opened up paperclip or fine screwdriver works.  Just push it into the larger of the two slots and push the triangular clip so it pops out the other side of the groove.  Push the clip so it rotates all the way out then pull it all the way out with a pair of pliers (grips).  You can sometimes pull it out with your fingers but it is quite a snug fit.

The replace it push the triangular clip in the main groove and align the flat ends of the wheel axel so it aligns with the smaller groove then take a scrap piece of hardwood moulding or a piece of plastic (the back face of a plastic rule works well) and press down hard on the wheel.  Initially the spring will compress and the block disappear slightly into the turret but push a little harder and it will bottom out and the glass cutter push fully into the back of the groove.

Changing over from the System 4000 you may not realise that when you insert a new wheel you may need to reduce the cutting pressure a little using the Allen screw adjacent to the green label.  Through the life of the wheel you will need increase the pressure little by little until it stops performing.  So this will need to be backed off when putting a new one in or it will score the glass far too deeply.

Lastly, apologies for being slow replying, new website and all it entails. ;o)