RNDP6000-100NAS bios upgrade after OS6 install

Hello everyone!  I'm new to the forum and netgear so bear with me.

I recently aquired from work the above 6 bay nas.  it hasn't worked in years due to a failed psu.  Well, if it's free it's for me!

the 4GB ram upgrade should be arriving today.  I've got new HDD's (also from work), and installed the new PSU (and extension cables) the other day to fire it up.

after all i've read on here about it, the one thing i missed was that the bios update is different than the OS update.. so i updated from 4.2xx all the way up to 6.10.x (latest stable release, not beta) as of last night... and then realized the bios is NOT part of the update.

I downloaded the OS4.2xx image but it wouldn't recognize it when i attempted to roll it back by performing the firmware update in the gui.  i figured if i rolled it back to 4.2xx then i can follow the instructions for uploading the bios..  

is there an alternate way with detailed instructions?  i can navigate around in linux but i wouldn't say i know it.

are there any utilities?   If i could just do a bios update to 'flame-v.whatever' that would be best but i don't know how.

if it's best for me to roll back the OS to 4.2xx, how do i go about doing that from OS6?

thanks!