To All
I do not have my MODEL28ASR yet, but do know about the 4 Bolts are used to secure the Typing Unit.  The Magnetic Screwdriver will sure help to install the 4 bolts.  
I am new to Green keys, but have been into Teletype since the 1960's in High School.
I am familiar with the Model 15 and 19 Teletype, so this Model 28 will be a challenge.
The one I will be getting is just like the Model 28 I had on a Navy Destroyer.  Go Navy.  Lots to learn.  73's and keep the oil can handy.  Al K8WXQ