It's a piece of cake (especially if you don't have the stock intercooler fan).
Put a (I believe) 17mm wrench on the bolt in the center of the tensior (facing towards the front) and turn to the right. The whole assembly will wrap up and around. Using your other hand, slip it off the alternator, and then release the tensioner. Then thread the belt out from all other accessories. Just make sure you have a good mental image of the belt route beforehand (or a sticker on the core support that shows it), otherwise it's confusing when putting it back on. When you're over/under all accessories other than the alternator, put your wrench on the tensioner, like before, and turn to the right. You should be able to slip the belt onto the alternator, and then release the tensioner.