So to sum it up.
The shortest way:
1. Dump NOR with memdump from XMB
2. Get per-console key (is there a way without linux? Nothing against it but I'm very lazy to just install linux, get the key, only to get the poor linux erased on the flashing the DEX firmware part)
3. C2D-it (and maybe check it somehow.. )
4. flash the NOR with jaicrab's self.
5. update to DEX firmware.