The tensioner pulley and the idler pulley just above it (IIRC) are the same pulley. You have to take the tensioner assembly off in order to take the tensioner pulley off. I think it's like three bolts, and it's not hard to do. I replaced the tensioner pulley, idler pulley, and belt in like 30 minutes. Shouldn't be hard at all. And there's pretty much no way to screw it up.
Ok, from memory, the belt goes like this: start at the alternator, go down and to the right to around the PS pump clockwise, back up and to the left and around the water pump pulley counter-clockwise, back down and to the right around the crankshaft clockwise, up and to the left to the tensioner counter-clockwise, down and to the left around the AC clockwise, up and to the right to under the idler pulley, then on upwards back to the alternator. If any of that makes sense.
I'm sure someone will chime in with a diagram soon. I just don't have one on hand.