There's nothing to know really you just reach in, unscrew the clear cap and reach in... there's a clip that is self explanatory to unclip and then you just twist until it pops out... then reverse the procedure.
To make it easier on the passenger side you can unbolt the air box and move it a bit out of the way. I didn't have to do this when I changed mine.
To make it easier on the drivers side (or at all possible in my opinion) unbolt the one bolt that holds the windshield washer fluid filler tube and move it out of the way.
You don't really have to change both if you don't care too much about slight colour difference, but if one is going chances are after all this time it's not a fluke and the other is pretty close to death too anyway.