What to do after a fail firmware upgrade ?

Hi all,

Today, i had the support on phone, and they told me that they can't do anything for me, be cause i've activated the SSH Commands, and installed OS6, so i could have made some changes that may conflict with the update.
Well, i didn't know, but making this caused my warranty to be useless :(

Anyway, they told me that my datas is still on the disk, and that i can retrieve them if i know how to do.
They told me that i need to go on the community forum to get some help if i don't know how to do it.

Actually, my NAS is on "support mode". This is the mode to allow netgear to check my nas files.
I have putty installed on my computer, but i'm afraid to do something wrong.

I'd like to do two things, and i would really appreciate that someone point me in the right direction to figure this out :
1 - I'd like to know how i can safely connect to my NAS, and copy/paste the whole datas folder via my local network to my computer,
OR, how to plug the disk on my computer (i have windows 7 and Ubuntu), and retrieve the data from the disk (which should be formatted as btrfs)
2 - Then, once first step is done, i will factory reset the Nas, and will never activate SSh again.

I would really appreciate, and can donate a contribution to the one who could help me to get my datas back on a safe disk.

Thanks by advance.