Thanks Vincent,
First, you should ensure you have a way to recover from problems:
Is your flash chip soldered or socketed on the motherboard ? If not, any failure (bad flashing or wrong coreboot) and you've got an expensive doorstop. If yes, do you have at least one spare compatible chip with an original bios flashed onto, to recover from failures ?
Flash is soldered, however I'm prepared to desolder it and install a socket. I also can copy original BIOS to other chip to have a spare. Fortunately I have required equipment here :-).
Then you're fairly safe to try, test, or hack on coreboot.
A serial console (to another host) setup and working is good to have, because VGA may not work at first.
I also have spare host to create serial console. However I really would like to talk to with a person who already tried this on Dell servers. I don't feel good enough in linux/C/PCs to be the first one who will install coreboot on a rack server. I did not think about coreboot before, but some time ago I saw a WIP for dell 1850, and this triggerd me to post to the list.
Best Regards, Michael W.