How big of a deal is it to replace/repair these parts?

I recently purchased a used Mazda5 2012 (110k mikes) and after driving it a few times the check engine light went on.

I took it to a local shop and they say that there are some bad sensors and they need to replace the intake manifold and vacume solenoid (something about a swirl sensor/valve) and that this will cost $1800 for parts and labor. (They also recommended new brakes and 2x new tires and wiper blades for an additional ~$1000)

I had the car do a pre-purchase inspection and the mechanic there only mentioned needing to replace the rear brakes (rotors and pads approx. $350) but that "I had some time on them"

Being fairly ignorant about cars, but eager to learn more, can anyone give me an idea of what's going on here and how serious these issues are? (Is the engine in danger in this situation?)

Many thanks!