Don't even think about removing it unless you have the manifolds off for access.
Otherwise, you can just about see it with something like a dentist's mirror, and just about reach it with your hand, both from below.
It has a 5/16" square female socket (ie not a standard socket drive size like 1/2" or 3/8").
I once made an adaptor to try to remove it, but in the restricted space I just could not exert enough force to move it.
It is in the owner's handbook as a routine job as if any owner could do it, but goodness knows why.
Don't worry. Flush the engine by disconnecting the radiator hoses and then sticking a garden hose pipe into a heater hose connection and blasting through.