Type 44 window glass problem

[Hale, Duane A WRAMC-Wash DC]

'86 5TQ.  Has anyone ever replaced the little black 'buttons' on the outside
of the front door glass?  These buttons are part of the "I"-shaped guide
that slides up and down the track in the window/door frame.  My front
'guide' broke off and I can't figure out how to install the new parts.  Does
the window have to come out?

Thanks!
Duane