Ray
The dual-pane windows of your vintage are notorious for seal-creep.  I redid one of mine myself.  Not a bad job, but a tedious one.  I was much too aggressive with the razor blade scraper and badly scratched the glass.  I "assumed" that tempered glass would be very scratch resistant.  Quite the opposite, it scratches easily.  So, if you decide to do-it-yourself, use a good lubricant cleaner to keep from scratching the glass.  I had the other windows redone by RVFogDR in Searcy Arkansas.  It was a bit expensive (about $200 per window), but they did not scratch up the glass like I did. 
Good luck with your window repairs.
Richard