This is what it looked like when the person brought it in.
One of the pieces was broken. A glass-friend had an almost similar glass panel I could buy from her and the owner and I decided to replace all the pieces of the same colour.
Most challenging I found was removing the lead. Very easy to break the glass you see :-) But nothing happened and after a while the glass was free of broken, and dirty lead and pulverised plaster which was used for making the window water tight. Dusty job as you can see here!
Before starting this I did read about the safety conditions working with (old) lead. For instance the dust from the old lead is very unhealthy and to prevent this dust flying around the lead cames and strips should be made wet before you start working on it.
Second challenge was cleaning the glass. I tried a few methods like rubbing with steel wool, soaking the glass in a water and soap solution, and in water with a dishwasher tablet in it, in water hydrochloric acid (mixed with water).
The hydrochloric aced worked best (with the worst smell....) but the glass was clean.
New lead was used to put the window together again and this is the result: