Best option is to remove the sash if possible and take it to a glass shop. They will have all of the necessary items other than the glass needed to do the replacement. The glass itself is cheap. Depending on the type of window, the accessories needed to do the job can easily equal the cost of the glass. On top of that you need to add labor. I wouldn't be at all surprised to see a bill for $60 - 75.00 for a 28" x 36" sash replacement.
All bets are off if it is one pane of glass in a double glazed insulated glass sash. In that case, the glass shop will have to build the "sealed glass" unit and then drop it into the sash.
