Denso sensors from RockAuto or buy Mopar.
They look like spark plugs sticking out of the exhaust, so follow the exhaust to see if you have 2 or 4. Then hit it with PB Blaster as they're usually on there pretty darn tight.
Click on the link
for different types of sockets.
I use this one and hit the handle with a hammer and or attach a breaker bar. (I've hit it hard and hasn't broken yet)
P.S Whether you have 2 or 4 it won't hurt to the buy the whole set. Just change if it's throwing a code or just change them all out for experience and exploration purposes
But DO NOT cut the wires unless you are sure you have the correct part. They have different lengths of wire and the harness plugs are not all the same.