It doesn't unscrew Chris. The focuser is a captive rotating ring with an internal spline and a mating one on the lens body.
I attacked mine with a junior hacksaw

, but since found that the internal plastic housing and focus ring will slide out. There is a washer half way down inside the tube that acts as a stop for the housing and the cable has a tie on it as a strain relief. Push the cable in a bit at a time as you withdraw the housing and watch out for the cable tie catching on the washer. I cut the SS ring off the front, but I'm sure it could be removed without damage (someone put it on there). Unfortunately I can't find the bits or the pics I had, just recently rebuilt the puter and they are on a backup disk, somewhere.
The main plastic housing holding the circuit board splits into 2 halves, so that might be a way of getting the front piece off intact. If you can separate the halves enough to get the circuit board out, the lens assembly will come with it.
Let me know how you go.
Cheers
Bill