There are 2 problems when changing the selector shaft seal which is leaking, removal of the seal in a tight area and to avoid damage to the seal area in the housing, plus not to damage the new seal on the sharp edges of the selector shaft when installing it.
There are some instructions online like this http://bmwe32.masscom.net/dutch740/s...ectorshaft.htm
Here a method I found on another forum: I attempted for considerable time to remove the selector shaft seal using various picks, small screwdrivers, etc. but was concerned that I would damage the housing or shaft. So after looking online for the correct removal tool, I made one by drilling out a brass bushing with a 13/32" = 10.318mm drill bit so that it would slide over the selector shaft (by using brass, I was not concerned about damaging the steel shaft surface). I simply screwed the bushing in, and when it bottomed out, the bushing came out as easy as can be. No need to remove anything other than the shift linkage. Hope this helps all others that need to fix this common leak source.
To install the new seal I used masking tape to cover the sharp edges of the selector shaft and then removed the masking tape after the seal was installed.