This is the Mazda 5 forum, but anyway you can buy a cheap obd2 reader from walmart and shut off the light yourself.
Your local Mazda dealer probably would do it for free since its almost a brand new vehicle.
The stem is part of the sensor, but the price is way too high, you can get a replacement sensor for around $30 on ebay or amazon and most tire places would probably charge around $20-$40 to install it.
You can either cut off the old socket and solder in new socket that you would probably have to source from a junkyard or buy a new harness, I think this is the correct harness but I could be wrong...
That is for the Camshaft Sensor, not the Crankshaft sensor...
The crankshaft sensor should be left (drivers side) rear of the engine block near the transmission, hidden by the catalytic converter and a cover/shield
Yes he said that is what he is going to do in his first post except walmart is going to reimburse him since they installed the battery, the battery was purchased at Costco but he had walmart install it...
Just did a quick google search and in many cases, particularly with the older mazda 5, this code often times turns out to be due to a faulty TCM (transmission control module)
something like these should work fine
https://www.autozone.com/license-plate-and-accessories/license-plate-mounting-hardware/proelite-anti-theft-license-plate-fastener/562428_0_0
You could try swapping the coil on cylinder 5 with a different coil on a different cylinder and see if the code follows, for example if you swap cylinder 2 and cylinder 5 and you get a P0202 code it means the injector was faulty, but first you should visually check the wiring
to the coil on...