removing the winsheild without breaking it is a serious chore. You need some piano wire or something thin and really strong which you feed through a point in the glue and then (with a partner) slowly pull it along the whole windshield. Of course, before that you have to take off all the trim, which isn't that simple either, and you have to get a clip kit if your car is older than a '90. What I did on my car a while back when I had these same rust holes was to just pull up (very carefully) the sections of trim where the rust was and then grind them down, paint them with por-15, and then I filled them with silicone I think or something of the like that was water tight. Then I covered it with body filler and painted, and it hasn't leaked since in about a year. I would try that first, before going to the hassle of taking out the whole windshield. Well, best of luck!
Nate Gundy
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'86 240DL, M46, K cam, 25/21mm sways