I'm guessing you are using Windows and do not have MobileMe. If I'm wrong correct me, and I'll give you the easy way. In the mean time.
Notes: In iTunes with the device selected, go to the Info tab and select sync notes for each device. If you want everything replaced on one of he devices go to the Advances section in the same tab and check the box next to notes. Be certain you pick the device that you want overwritten, or you'll lose your notes.
Contacts: You could do this here also, if you have a contacts manager on the computer you want to sync with. I recommend setting up a Google account instead and using it to sync contacts between your devices, and the computer if you like. You have to set Google Mail up as an Exchange account to sync contacts. These are the instructions. If you already have a GMail account set up be sure to either delete it or turn off the options (Mail, Calendar) before creating the new one.
Setting up Google Sync with your iOS device : Google Sync (ActiveSync) - Google Mobile Help
Audible Books: In iTunes on the computer, make sure the books are showing up under Books in the Library listing. If not, right click on the files in iTunes, choose Get Info, go to the Options tab and make sure the Kind is set to Audiobook. Under the sync settings for Books, make sure you have sync audio books checked.
If you are getting an error about authorization, the Audiobooks may be linked to an Audible.com account instead of iTunes. Make sure you can listen to them in iTunes. If they aren't authorized it will ask you for your Audible.com account. You'll have to enter that info. Once the computer is authorized to play them they should transfer to the device without a problem.