Would cheaper used parts work just as fine ? *CHEVY MALIBU 2008*

I recently bought a 2008 Chevrolet Malibu for 1500$ Canadian. Everything is fine except for the “camshaft Sensor” and the “Front lower left control arm “. The garage I went to is asking me 220$ for a new control arm plus 80$ labor fee which seems reasonable. And 110$ for a brand new camshaft sensor plus 80$ labour fee which again seems reasonable.

However, I’ve been thinking if it would be worth it for my pockets to just buy a used Front Lower Control Arm and camshaft sensor from a used Car Parts store instead of a new one, like the car is already old it self why the brand new part you know...

I’m Still new in car world, those of you with more experience what do you think ? What would you suggest ?

Thank you in advance 🙏

Ps. The mechanic also said that “the rear suspension is rusty and will need to be considered to change soon” how serious is that ?