My ReadyNAS 104 died due to lightning - how to recover data

It could be just the power supply.  But a strike that close can often induce a voltage between the ground of the LAN port and the power, which could fry the LAN connection as well.  Your fried router is a sign that could well be the case.  You could try another supply, but I'd say your chances of that working are less than typical. It may boot, only to find you have no way to access it because the LAN port is dead.

Of course, if you are going to replace the NAS with another ReadyNAS if the replacement supply doesn't fix the problem, you'd already have a new supply and could include NAS without one in your search for the replacement.