I use the sting thing all the time (untill recently) and it does make installing a window very easy.
I have never lost a window on the removal untill I removed my crewcab one. It was going fantastic, 85% out then just fractured due to a tiny delamination on the bottom of the screen.

Two proposals I would recommend if you have not done this before, phone a professional, it will be cheap and if they break the screen they will have to replace it! Get a new rubber and cut the window out of the old rubber.
Dickspanner