I can't guarantee that your purchases will be accessible after a restore. I didn't have any and I was willing to start from scratch if needed. Would be nice if someone could chime in... They might restore, but be unplayable until you connect to Sony's servers or something, which you would need the latest firmware to do.
y2jb has been updated with p2jb. The 10.01 is for running a different exploit, I believe that's Poopsploit, which is what you can run after unpatching the bluray drive. It didn't work after 10.01 due to the BD being patched and doesn't work after 12.00 because the exploit itself was patched.
Modded Warfare on youtube has a good recent guide on how to do it.