Door Glass replacement

[Triple-S]

Although the door-glass carriers on my 140 are almost new one window has become detached from it. The gasket strip along the join also looks new, so I searched both on here and in the manuals for advise on how to refit but couldn't find anything.
Questions: does that section of the carrier have to be prised open to accept the glass plus gasket; how to clamp it shut or bash it together after installation without crunching the glass, and what adhesive to use (if any).
I'd prefer to do the job in-situ but assuming it will pass through the gap at the door top then so be it. Has anybody else done this job - john-h perhaps, as I'd be grateful for advice.

Paul