Just what he said,the nut holding the wire on is a 10mm,the 3 bolts holding the alt on are 13mm,use a long 1/2 inch ratchet with a cheater pipe to get the belt off(the cheater pipe just makes it easier). An alt will run ya between $160 to $200.You will need a 1/2inch drive breaker bar to release the tension on the belt. You put the breaker bar in the spot on the tension pulley and pull the breaker bar this will release the tension on the belt then just slip the belt off the pulley.
The big wire on the back of the alternator under the cover of that wire is a nut. You will need I believe a 3/8 socket maybe a 10mm to remove the nut and then the wire will come off.