Is there any way to install m0n0wall without any keyboard or serial access?

I have a number of Toshiba Magnia SG20 machines, so I am trying to 
configure m0n0wall on them.

** I have the image installed on the hard disk, but can't get the 
Ethernet ports configured.

There is no serial port.
There is no USB or PS2, so no keyboard access.

There is an LCD panel on the front, which scrolls the boot messages as 
if it were a VGA monitor.
It stops at "Enter a number:"

I have Linux installed on another of these machines and this is the 
'lspci' report on the Ethernet controllers:
00:08.0 Ethernet controller: Realtek Semiconductor Co., Ltd. 
RTL-8139/8139C/8139C+ (rev 10)
00:09.0 Ethernet controller: Intel Corporation 82557/8/9/0/1 Ethernet 
Pro 100 (rev 0c)

I found an earlier thread where it looked like someone was able to get 
m0n0wall to automatically detect the NIC and he was able to use the web GUI.
It looked like the specific controller made a difference which allowed 
m0n0wall to just work with it.

I can install the m0n0wall disk as a second disk in my Linux system.

** Is there a way to choose one of the above NICs by mounting the image 
in Linux and editing something?

Is there any other way, like some sort of a rebuild of m0n0wall?
That sounds like quite a bit more involved, so of course easier is better.

I just had another thought: would I be able to mount the disk in a 
virtual machine and configure it? I don't currently have any virtual 
machine, but would be willing to try and set one up if it might work.

Any suggestions are appreciated, as always.

Thanks in advance,
Joe