Inspiron New Motherboard

Hello, I'm new to this board.  I'm trying to repair my Inspiron 660s slim desktop with Win 7 Home Prem.

After testing all the hardware, including the HD, PS, Memory, Monitor, Cables, etc. have determined the Motherboard is bad.  Tried to purchase one from Dell, but all they had was one for Win 8.  Dell CS did give me the part number of 478VN as the replacement for the OEM Pinevalley MB

part # as it appears on the MB:

11061-1

DIB75R/Pinevalley Motherboard

48.3GX01.011

Having found a NEW 478VN I preparing (tyring to learn what I might have to do)  to put things back together, while I wait for it to be shipped.

My question is:

After installing the new MB, will I have to re-install Win 7 OS or would there be a chance that it will boot without have to go through the re-install.............????????  OR

Is there a process for installing a new MD to follow without having to re-installing the OS.....?????