When I had mine replaced, I was able to check in on the technician's progress and ask him questions about the install along the way. For instance, I had done a fair amount of research regarding the windshield trim clips, which occasionally seem to be difficult for installers to even find, and spoke to him about whether or not he had any replacements, and the possibility of removing the trim altogether and installing a gasket surround instead. The technician seemed to respect and appreciate the familiarity I had with the procedure and I'd like to think that had a positive effect on his work. I wasn't hovering over him while he worked, but I showed interest and understanding while letting the man do his job.
Hope that helps.