Update only a specific folder in a sparseimage ?

[Wanda]

Hi,
I have created a full backup of my main HD to a sparseimage on a second internal drive.
Since I created that image, I upgraded to 10.4.4, installed iWork and iLife '06 and added new photos and music to my iPhoto and iTunes libraries. Somehow one of the Apple updates messed up with my current installation and I want to revert back to my backup. I don't mind reinstalling iWork and iLife.

However, because I added new photos and Podcasts that I don't want to download again, I'd like to update only those folders in my sparseimage, so that I won't loose that data when my backup is being restored.
I don't foresee any problem for iTunes but it might be more tricky for iPhoto considering that the latter was a major upgrade that also update the library file.

Do I need to create a custom script if I only want to update my iTunes folder to my sparseimage for instance? Can I just mount the sparseimage and replace the folder in the image with my current one?

I am a bit lost here and any help or hints would be greatly appreciated!

Thanks
Wanda