The following images (click on them for larger versions) show how the objective focusing mechanism is attached.
The compenents here are the circular dovetail which accepts the objective turret, a space below the objectives which accepts a linear dovetail which can contain a beamsplitter and filters, the rack which interfaces with the drive pinion gear and a lens which is for the front camera port.
It attaches to the body with four bolts from the top. It must engage the rack and pinion properly before tightening the bolts!
Next, I replaced the prism and mirror slider assembly.
for navigation!