[68JOHNDEERE]

Mark on the old glass the edges of the track before removing it, then measure on the new glass to center the track onto the new door glass.
To remove the metal channel off the old glass I like to use a 2 inch square piece of hard wood. Lay the glass flat on a table while someone holds the door glass, using the wood and a hammer hit the metal channel off away from the glass.
If you have a local glass shop they may have some tuff pak channel bond tape. Wrap that over the lower edge of the glass and hold it in place with strips of electrical tape. Cushion the table with a couple layers of cardboard, stand the glass on it's upper edge on top of the cardboard, then with a little glass cleaner on the tuff pak tap the metal channel onto the new glass with a rubber mallet til seated fully.