Here's a schematic, courtesy of brownell's:
http://www.brownells.com/aspx/ns/sc...8&m=22&mn=AMT®&model=Back-Up+DAO+Large+Frame+
You would drift out with a punch the "firing pin retaining pin",#12, and that should free up the firing pin so that it can be removed.
I would do this with the slide off the frame, and you can then use a brass punch to knock the pin out from the breechface, if necessary.
Something could be binding it up in there, such as: Old gunky gun oil; factory burrs causing a hang up; broken part...
The cheap and easy method would be to spray a degreaser in there, such as GunScrubber or Brake Cleaner, to clean out any gunk that might be causing the bind - but regardless, you should disassemble the entire firearm and do a detail clean.
I have the DAO .380 and I had to take some Wet/Dry 600 grit sandpaper and de-burr/polish/smooth quite a bit of my pistol because it had some minor issues.
I rolled up a section of the sandpaper into a tube, got it wet, and polished out the firing pin channel on mine - there were a lot of machine marks on my .380 and it REALLY needed cleaning up!
Also, the .45 DAO came with 2 sizes of firing pin tips, one a .060 and the other a .088 old model; if someone put an .088 tip in your .060 gun, it would get stuck.
