First you need to install hfsutils. Once these are installed there should be a number of tools for mounting, reading, writing etc to an hfs volume.
Then you need to mount the volume as root using
This is where I get a little fuzzy because I have a similar but more complex issue. I am trying to automount an external drive using the fstab.
sudo mount -t hfsplus /dev/(your drive) /path/to/mount
After some research, it turns out that hfsutils cannot mount a journalled HFS+ filesystem with write access.
My search continues....