A couple of careless seconds to break ... a stack of careful minutes to repair.

It is possible to spend an entire Saturday morning replacing broken glass ... the bulk of the that time was probably spent acquiring the new glass. The trim pieces which hold the glass had to come out and be sanded ... I kept the brads in wherever possible, but ended up adding new finishing nails anyway so it really didn't matter. Next step was to clean out old putty ... scrape and sand ... there were tiny splinters of glass mixed in too.  Then, apply a nice pad of DAP.  Some people use points to hold the glass in  place, but I think the adhesive putty does just fine (plus I have broken many a pane if glass tapping in points ... and doing this little job reminded me of how much I love my new windows!) Next ... the tricky part and I was very happy to have some help here.  All four of the trim pieces had to be aligned and wedged back in to place together.  I would have tried to fit them one at a time culminating in a big fail ... they simply don't fit unless they are "snugged" all together initially  and coaxed back in with a sledge.  "What?! A sledge hammer!"  I was very surprised when L asked me to go get it from the garage.  He said the weight of it would save time and frustration.  The pieces did fall to the floor several times. Once the pieces were "in" I was able to push them all the way back to the glass with my hands.  Then I tapped the finishing nails in to place and cleaned up the putty which was pressed through on the inside.  The area will need to be wood putty-ed and repainted to finish the job.
A couple of careless seconds to break ... a stack of careful minutes to repair.  Three made that little hammer in some High School shop class ... I enjoy working with it.