notepad++ supports editing binaries and leaves everything you didn't modify as is
But you can't change the size of the text in the nx3 file, if you just need to change the dds to a new one, rename the new one to have the same name size.
For example:
Code:
asf_warrior_master_body.dds
asf_warrior_master_bnew.dds
If you can't have a file with it's name size equal to the old one, you can't do raw editing.