There is a tiny clip that holds the lens in.
This thread and pictures (pic 1 in reply 1, pic 17 in reply 2) should give some good clues on how it is assembled. https://www.vacuumland.org/cgi-bin/TD/TD-VIEWTHREAD.cgi?34091_7
I ~don't think~ you have to remove the belt lifter assy from the nozzle, but I could be wrong - it has been a while since I did this.
Tweezers will be a tool of choice.
