Usually, you do not need to remove the motherboard for a simple cpu replacement.
that is, if you have a modern case with an opening in the motherboard mounting area so you can see the back of the motherboard.
First of all, a tip:
Run the cpu under load and shut down just before you try to remove the existing cooler.
That softens the thermal paste and makes it easier to get the cooler off.
Clean off the old paste with alcohol from both the old cpu and the cooler.
Insert the new cpu and remount your cooler using new paste.
Most of the time, you will need that opening to access the back of the motherboard.
Either to secure a backplate, or to verify that pushpin coolers have all of the pins through and locked.
Before you