Duster windshield removal/replacement

I have a leak in my 1971 Duster - I’ve had it for many years and it is coming from the windshield on the left and right edges. I had a new windshield installed over 10 years ago by a local glass shop and it leaked after a year or two. I’m assuming they didn’t use the correct “stuff” around the windshield. I talked to a local restoration shop about pulling the windshield and re-installing with the proper sealants. They said the risk of breaking the windshield was too much for they to attempt the job. Is this a reasonable assumption? I just checked and it looks like I can replace a broken windshield for less than $500 - so maybe I’m willing to take that chance. Questions are as follows:
1) What is the correct sealant for the installer to use if the windshield is removed and re-installed or replaced?
2) What’s the chance that a good shop could apply sealant to the existing windshield and stop the existing leaks?
If you plan on installing a new gasket, then just cut the old one with a razor blade box cutter and remove the windshield yourself. If you're keeping the old gasket and it cost more than a new windshield, try pulling the windshield and if it breaks, oh well, get a new one. I find using a wide putty knife and carefully peeling the gasket lip on the inside over the pinch weld to be the easiest way to remove the windshield without breaking it if you need to save the gasket. I like to start at an upper corner and work my way over to the other upper corner. Then work evenly on each side to gradually get to the bottom corners. Usually by that time. the glass with gasket will lift out.