Almost bricked my N2100

["Frank A. Kingswood" <frank@kingswood-consulting.co.uk>]

Hallo!

Through no fault of my own (obviously!), my Thecus N2100 no longer has a 
working initrd in flash. On bootup I get:

  RAMDISK: Couldn't find valid RAM disk image starting at 0.
  No filesystem could mount root, tried:  cramfs
  Kernel panic - not syncing: VFS: Unable to mount root fs on 
unknown-block(1,0)

I have access to RedBoot and have successfully used TFTP to download 
files into RAM, so to me it looks as if it should be easy to recover from:
  load -r initrd -b 0x00800000
  fis load -kernel
  exec -c "console=ttyS0,115200 root=/dev/ram0
           initrd=0xa0800000,42M mem=128M@0xa0000000"
and then force the initrd to be rebuilt and re-flashed.

I have two questions for you, my learned audience:
1. Is there a ready-made initrd in one of the debian packages that is 
more-or-less usable with the standard (and up-to-date) Debian distribution?
2. What do I need to do in terms of dpkg and apt commands to force the 
initrd and kernel to be reflashed?

Many thanks in advance,

Frank