broken home folder - how to log back in ?

Hello, I'm having serious issue on my MacPro 10.7.4, as I can't log in any more.

Issue:

My setup:

• System 10.7.4 on MacProSSD (internal SSD)
• Data on my software RAID0 on 2 internal HD.

Unfortunatly I had the bad idea to move my home folder on the RAID0 cluster.

One of the 2 hard drives just died, making impossible to reach any data on this side !

So now, I just get an error trying to log back, as I guess the system can't find my home folder.

Tentative:

I just set up a second partition on my SSD, installed lion again and boot from here.

So I can have access to the original SSD file system.

I'd like to modify some files to update the path to a new home folder. (not on the RAID obviously but still on SSD).

Could be done by terminal / command line...

I used to know how to do that on linux by modify /etc/password, but I can't find the same files on OSX.

Question:

Do you have any idea on how to modify / update the system user path, so I could boot again from by previous partition ?

Thanks for your help !