Is it easy to change the battery in a Toyota Camry?

Yeh its usually not complicated. Some newer cars are making it a pain in the ars to get to the battery but usually you'll need either a 1/2" or 13mm wrench or an 8mm wrench and a ratchet with an extension and 8mm socket. You can probably find detailed instructions at wiki how or something but i'm not doing all the work for you. basically you always start with the negative - (black) cable first. loosen the nut or bolt depending on the terminal style and move that cable, then do the same with the positive +(red) cable, then depending on the set up you'll have a battery hold down. in most cases it's a plastic wedge at the bottom of the battery usually with an 8mm bolt, sometimes the bolt is made long to reach around the top of the battery sometimes it's not thus the need for the extension. hope this helps