Remove glass from old door
It depends on the chemicals used if the glass can be damaged. Removing the wooden strips holding the glass should be sufficient to take out the glass. 
After the strips are removed you should carefully verify if the glass is completely free.

Paint remnants could still hold the glass.
If so you have to loosen the glass very carefully not to break it.

Push the glass carefully from below with little pressure upwards and watch it move. If not then you need remove old paint as good as you can and try again. Go along the whole window that way before trying to lift the glass from the door frame.

Be carefull not to break the glass and good luck