Hi
You don't say which model Ducato you have?
The owners manuals & other manuals for both the X244 & X250 are available for the download section of the forum - https://www.fiatforum.com/downloads.php?do=main&perpage=20&categoryid=22
If you are looking for earlier versions - X230, an English version appears to be very hard to find, there are manuals for the early 280 models around.
Cheers
You could always try this crowd. They are in French but the exploded diagrams etc. would be helpful if you had any idea what you are doing at all. They also do digital editions which means you could possibly use Google translate to get them into English.