The window comes pre framed and mounted in metal. If you replace it yourself, you will need to remove the arm clips, let the arms loose, then lift the widow carefully up to disengage it from the hinge. The new one then will be put into the hinge channel, and arms re attached.
You probably need two people and two step ladders to do it safely.
Or, if you are near a dealer, and the lawn company is paying for things, they will do it too. But it is not hard to do yourself, once you have the window.