The windows were done by a professional Andrew. Like you I was not game to touch them. Hard to know the exact cost as I got the rear quters done at the same time, but it was probably around $3500 including paint. Words of advice would be:

Make sure you get plenty of opinions, ask lots of questions
don't even bother with smash repair people
Make sure they have done them before
They need to spot weld around and around and around the join at intervals so as not to warp the panels this keeps the heat down
Resto places are the best bet
No need to cut a whole panel or replace the whole roof as some suggested
I also got the side supports out of an old wreck which helped as they went straight in and therefore I did not have to get them made up.

I saw a van at Hanging rock yesterday that had the same treatment and there were cracks in the bog coming through. Having seen mine done close up I reckon they will go the distance as there was very minimal filler applied, probably no more than if trying to get a windowless van perfectly straight.

Thanks for your comments abncraig.