Here's a way to install a tongue-and-groove ceiling without damaging the wood. Set a board in place. Then with a scrap piece of tongue-and-groove stock as a block, give the board a firm tap. This forces the tongue tightly into the groove. Using finish nails, secure the backboard in place. All the tongues remain intact and undamaged if you use a block.
For more on ceilings, consider:
5 DIY Wood Wall Treatment Ideas
Top Tips for Installing Tongue-and-Groove Paneling
From Finland with Loves: Notes on Installing a Wood Ceiling