?? if it is only the pulley /bearing you want to change...THE BOLT THAT IS IN THE CENTER OF THE PULLEY IS LEFT HAND THREAD!!! if it is the whole tensioner you want to change,,,disconnect battery negative,Drain coolant!! remove alternator, ...one of the alternator bolts holds the tensioner on, then there are two more bolts.. heater core coolant goes through this too! spray the plastic elbow that goes from the tensioner to the front of the intake manifold and also the tube that is under the tensioner with good penatrating oil, pry and wiggle very carefully straight out (I broke the plastic elbow on mine) clean holes for coolant and make sure you get new o rings, put engine oil or vaseline in the holes for the o rings.
You really don't need to drain the radiator- only about a quart of liquid will escape. However, be sure the coolant is cool before attempting this! Otherwise have an ambulance standing by.
Pull the tensioner assembly directly towards the radiator, don't twist or rotate it. Even being VERY careful the plastic tubes will probably break. They get brittle from heat. It was a terrible design choice but what are you gonna do they saved maybe $0.50 a car over Aluminum tubes.
They are a dealer item, about $20 for the pair including O-Rings. To be safe, I recommend you replace those plastic tubes when you replace the tensioner.
Also, if the plastic tubes break off inside the housing you'll need to get out the pieces before replacing them. Be careful not to damage the housings.