I do not know how easy or difficult bacula or any other program is. This only relevant with personal choices. So something that is difficult for you can be not as difficult for someone else. You can also use Amanda
for the same. But it still depends how comfortable you are with Linux and commands and editing files.
On your second issue of configuring Linux as PDC, you have some support with SAMBA. Not just Ubuntu, but any major distribution will support the same. All you need to know is how to do it. But if you are handling windows clients, windows server for Active directory is better with far more options on handling clients. If you are just looking for basic authentication and authorisation for network resources, SAMBA can help, but on the other hand, if you want more granular control, windows is what you are looking at.