Robert, unfortunately you took the hard way to replace the fans. I just changed out the driver side fan on my 1991 350SD just last month. They recommend replacing both fans at once because of the aggravation involved in removing the aux fan shroud. I chose only to do the fan that was failing.
As in an earlier post, I took out most of the rivets. Many of them broke because of the age. I just pushed the broken ones through with a screwdriver, gently. I bought all new rivets at the dealer, rather cheaply.
Once the rivets are out, I then removed the small air shroud to the air cleaner on the lower passenger side.
I then gently pulled the aux fan shroud from the bottom and worked it up - as the aux fan shroud has a lip that sits on top of the fan assembly. Once I gently worked the plastic up and over the fans, I was able to remove it and then the fans.
This took me about one hour to do, however, I was on business traveling and did it in the parking lot of the hotel - with minimal tools.
With the driver side fan failing in 100 degree weather, it definitely had an effect on cooling when in around town driving.
Just posting this to help anyone else who has to do this.
I finally found that by taking out the radiator and condenser upper retaining springs and then pushing the condenser top back the thickness of an open end wrench (1/4"-1/2"), which I used as a wedge to retain it in position, I could remover the shroud -- then the double fan assembly.