If you are just changing the pulley remove the belt and weasel a hex key into the bolt on the pulley. If is the tensioner assembly. It is a different story. The repair is very straightforward. I would suggest removing the radiator to gain clearance even though some may tell you it is not necessary. The radiator removal is a bit of a chore as there are two hidden small bolts at the bottom that attach the radiator to the a/c condenser which are difficult to remove. If I remember correctly, the power steering pump must be unbolted and wrestled out of the way and a bracket that attaches to the water pump. Definately replace the tensioner shock and serpentine belt while you are in there. The tensioner assembley is around $100 and the shock is about $12 and belt is about $35 USD. The belt is a piece of cake with the radiator out, and a real pain with the radiator in the car.
If you are a real glutton for punishment and a competent DIY mechanic you may consider water pump replacement while your in there. It is the next step if your water pump is suspect. Though you would be a genius to figure out how to get the water pump bolts out. It is extremly difficult to get those back water pump bolts if it is your first water pump on a 2.6.
1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T