I did mine a couple times. Hated it. Then I found the real solution.... take it to the bus repair shop and have the insurance take care of it
Actually, the real trick is to buy the spline tool that is use to insert the spline, and use a good soapy solution to lube it. I watched the guy at the shop put mine in, and he made it look easy. Of course, he does them often.
We did find that when I put my fiberglass windshield frame back in, somehow the openings shrunk a bit, and was interfering with the glass. The last time I took it in, I had to have both sides replaced, and they had to do a bit of grinding on the opening to get better clearance. Then it was not a problem.