JTAG

[Manaslu]

With my Guruplug stuck, I need to try the JTAG interface. Being a newbee on the JTAG, I have tried to find basic explanations:

What Windows program to interface with it.
What can I expect when I have it lined up:
*  promt
*  command set
*  possibilities to work with Linux (Debian) (like editing files, a.e. fstab where my boot problem seems to lie)
*  reboot the plug
*  reload the OS

All I can find is articles that seem to start at an advanced level.

I can find my way in Linux, and are pretty well at home on the NSLU2 but the JTAG seems to be out of my reach at this stage.

Who can help me on my way by pointing at some down to earth JTAG/Guru/Sheeva primers?

Thanks!