Can't change permissions

[Ja Di ksw]

So, long story short, I tried changing the permissions on my external hard drive to "Read & Write" and apply it to enclosed items. It was too much, Finder relaunched, and now the entire drive is set to Read Only. What's odd is it says "Read & Write" under info on many items, including the drive itself, however right below "Sharing & Permissions:" it says "You can only read". I can click the lock icon, and it prompts me for my password, but I still cannot click anything under Privilege after I enter it. The "Name" looks greyed out. If I try to use the Disk Utility on it, verifying and repairing permissions is greyed out. Repairing the Volume tells me it can't, that I can still read the data but not change it, and that I should reformat the hard drive. However, I don't have enough space on another hard drive for everything from this one, and many items are things I can't lose (wedding pictures, important work files, etc). When I try to use Terminal with: diskutil repairvolume /Volumes/[Volume name]/ it tells me: Usage: diskutil repairVolume MountPoint|DiskIdentifier|DeviceNode
Repair the file system data structures of a volume.
Ownership of the affected disk is required.

Any idea how I can fix this? Thanks in advance for any help!