Yeah, usually is the NAND.
It's pretty hard even for the experienced user, and impossible for the regular user. Also, you have to get all the data from your NAND, and inject it with another NAND. You have to match the keys for all I/O to work properly as you cannot use the original keys from the other console. So yeah, it's pretty much impossible...
You could try it, but if you don't have any experience with micro soldering, most likely you'll kill totally the console.