My dealer has said lens for sale and I offered to fix stiff near range focus and while at it I decided to clean the accessible, quite dusty lens surfaces too.
This is a simple 5 elements in 3 groups construction.
http://cdn-10.nikon-cdn.com/pdf/manuals/archive/Micro-Nikkor%20105mm%20f-4.pdfUnscrewing the tiny lock screw hidden behind the slide-shade enables unscrewing of the front outer barrel/shade. In the rear a 5 screw removal takes care of the opening from behind. Splitting the lens assembly between the 3 forward and 2 rear lens elements three screws need to come out.
The aperture blades were clean and needed no further attention. Re-assembly can be a little tricky in order to the the aperture levers correctly connected.
Here are a few shots showing the disassembling process.
