Well, when the BIOS is being updated and the power is interrupted it can damage the BIOS beyond repair, and leave the motherboard useless... so when you did the hard restart, that would be the same as interrupting power... what's not clear is the image; did you take that shot before starting the BIOS update, or is it what you're getting now?... I would guess this is now?.. If so, the update may still work, but what can you do without a keyboard?
If you have to replace the motherboard, you should use the same exact model as replacement... they may have mentioned the chipset to you because using a different motherboard may deacivate the OS. Besides you can't replace the motherboard with another make because DELL has their hardware made to their particular specifications and component arrangement that make their motherboards close to impossible to replace with any other make.
The 0X501H motherboard for example, has differences that make it different from any other motherboard made (except maybe other Dell motherboards).. It has no mouse and keyboard PS/2 ports, as you can see in the image.. they must be on a PCI/PCIe card, and the I/O plate cant be used with a different motherboard unless you drill the appropriate holes on it, but that's only one difference, it may also have different front panel connections, so Dell makes sure no owner can replace the motherboard with any other make.