I'll skip over the part that says that Windows Home Server is "OEM" software and moving it to a new motherboard is contrary to Microsoft's End User License Agreement. The EULA does, however, allow replacement of the motherboard if the original has failed.
You should be able to move all the disks to the new motherboard (being sure that the old "System" disk is listed as the first hard disk in the BIOS boot order). At that point, if you boot to the WHS Install DVD, the WHS installer should see the old WHS installation and allow for a "Reinstallation" of WHS.
That'll be a complete re-install of WHS on top of the old installation and it will keep all your shared data folders as-is. I don't recall what it does to your client PC backups. If you absolutely don't want to risk losing previous backups, you can back up the client PC backup database to another disk(s). There are complete instructions for this available. I've done it a couple of times without incident.
You can find complete instructions for these operations in the Microsoft WHS whitepapers and on http://wegotserved.com