Ducati USD fork legs

[Imagineering]

Can someone please help me with stripping down USD Fork Legs. I'm familiar with standard Legs and need to know how these come apart before starting on them. The Bike is a 1991 Ducati 400SS with 41mm USD Forks marked 'Ducati'. No other information on them, could be Showa or Marzocchi ?
I've undone the Fork Caps, but they only come out 15mm and then just rotate without coming out of the Leg.
Need to replace the Fork Seals & Head Bearings for Compliance

Thanks in advance.

[nodrog:Me]

Push the outer leg down and undo the nut holding the top cap on. You will need to make a couple of simple tools. Google is your friend.

[Rhys]

Try http://www.teamyikes.com/SuperSport/sssuspension.html

[Imagineering]

Thanks Guys, should have Googled earlier.

Problem now is that wherever I search, Google, YouTube etc, I cannot find the Oil Weight & Quantity for the 400SS. The Forks are SHOWA, branded as Ducati and are non-adjustable.

[Rhys]

I don't know if the 400 is the same but 900ss is 440 cc and the 750ss is 457cc of ATF SAE 10w20 or fork oil SAE 7.5