I've thought about installing those automatic foundation vents but was
uncertain as to how difficult installation would be.

The current vents in my crawl space are nothing more than one cinder
block placed "sideways" to allow the openings to be exposed from
outside to inside.

I guess I would need to purchase a small circular saw with masonary
blade to cut out these vent blocks.

It appears like the foundation vents get mounted from the sides by some
type of fastening method.

Ever install any? If so, exactly how difficult a process.