I installed my own springs in 6 hrs w/o any airtools, so with the proper equipment one can easily do it in 3-4 hrs.
The reason why shops are quoting so many hrs is because most of them have never done this before, and by law (at least in NY), shops cannot charge more than their estimate unless they get permission, so I think they just want to play it safe.
I am moving to Houston in a month, so I'd be happy to assist anyone in the area
