First thing you need to do is see if your tensioner uses a lower plastic elbow. Some where between 97 and 98 they started using a lower and upper plastic elbow.
You will need a new lower elbow or lower o-ring depending on which tensioner you have.
Here is a picture of a removed tensioner from a 96 L36 that does not have a lower plastic elbow. The lower elbow on the early tensioners were part of the aluminum casting like in this picture.
You open the drain on the bottom of the radiator and let all the coolant drain into a pan.
Remove the negative battery cable.
Remove the serpentine drive belt
Remove alternator and front brace taking note of where each bolt goes.
Remove the two heater hoses from the tensioner pipes. If you remove the tensione pipes from the tensioner you will need to replace the rubber o-rings.
Now remove the two bolts still holding the tensione on. One bolt is hid out of sight on the left hand side of the tensioner.
Once the bolts are temoved gently wiggle the tensioner till it comes off.