There are a couple issues here. First is legal. In terms of Windows licensing, a new motherboard is considered a new computer so a new Windows license will be needed. The exception is when replacing the old board as part of a repair action because of failure of the first board - then it is legal BUT the boards must be identical, or the recommended replacement by the original board's maker if the original board is no longer in production or available.
In other words, you cannot "upgrade" the motherboard in the process and use the same Windows license. The exception there is if the original license is a "full Retail" version, as bought separately at a retail outlet.
As far as the RAID controller - in theory he is right. But theory and real world don't always jive. For certainly you would have to be certain the controller is the exact same model and revision number, and that may not be easy to determine, especially before purchase.