I did the front and rear on my 69. If you use the 3-m strip kit and you have a helper to help you set the glass in the body, its pretty easy. I did the back glass by myself, but you need help with the windshield. If you have access to some suction cups for installing glass, and a helper, it would really make it easy. If you dont want to use the strip method, then you should probably take it to a professional installer so they can seal it with urethane. the strip method is the way it was done in 69, but the urethane is a better way to go if you really want safety and better sealing against leakage. I wont be driving mine all the time, so I felt like the strips would work fine for me, plus I wanted to do it myself.
Also, if they are not already installed, you need to put all the molding clips around the winshield and back glass openings before you install the glass. Hope this helps.