Look at the tensioner arm. The square hole accepts a half inch drive ratchet or breaker bar. Use it to relieve tension on the belt and slip it off of the pulley. Remove the belt, install the new one using the belt diagram under the hood, leaving it off of the tensioner pulley until last. Use the ratchet or breaker bar again and slip it over the tensioner pulley.
Best place is to keep your engine problems right here.
Using the DIC, a fully charged battery at Key: ON should show 12.4 to 12.6 volts. During cranking it will drop a bit, then, as the engine starts and comes up to fast idle speed the voltage should ramp up to 14.2 - 14.8 and stay there for a while. As you drive and the battery approaches full charge the amperage (you can't see that) will ramp down and voltage should stay at 14.2 or somewhat higher - the voltage regulator ALWAYS maintains a slightly high system voltage and varies amperage to that required to run the car and maintain full battery charge.
Engine OFF, using a VOM, battery disconnected from anything (cables off) it should read 12.6 volts.
If the battery is more than 5 years old it's on its last legs. Group 79, sealed vented, at least 800 CCA.
If a "12 volt" automotive battery reads 12 volts or less it's essentially dead - there's some surface voltage on the plates but there's no cranking ability. Google "automotive lead acid storage battery theory" or somethig close.