quartz calibre do have a battery but also have a series of rubies, cogs pivots and lubricant between the pivot and the ruby. every now and then, the calibre needs to be cleaned and oiled to live long. this can take place at battery replacement time. This could be why the price may seem high. Otherwise, a simple battery change is done in 15 minutes and the baterry itself cost 5 usd at the very most.
in some JLC boutique they have a dedicated watchmaker that does it in no time and for a modest amount, but you may live far from one of these 30 boutique around the world.
now if you want to open the case of your reverso on your own, this is probably not the type of watch to start experiencing with as opposed to simpler cases where teh correct tool allows you to remove the back case with no problem and change the battery in no time. the reverso case is made of 50 parts and you may scratch your case not willingly.