need help re: firmware update for WNR2000v5

> [...] Any advice on whether I need to try the update via my wiFi
> connection or whether I should skip the firmware update?

   I'd try to find a friend or colleague who has a computer with a
working Ethernet port, and use that to do the update.  Once the firmware
kit is on the computer, you don't need Internet access; all you need to
do is connect a cable from the computer to the target router, and follow
the update instructions.