[Plugin : Fancybox for WordPress] Display custom fields

Hi, (I’m french, my English may suck)
I’m working on an art gallery website, where 1 picture = 1 work.
I’ve made some custom fields for the works (such as price, painter’s name, etc).
I’m trying to display my custom fields in my Fancybox when it opens, instead of just the title.
Is there a way to do it ? I understand php a bit, but JS is chinese for me.

The concerned page : https://collectionsiparticuliere.com/?page_id=317

I’m using WP 3.4.2, Fancybox for WordPress (3.0.2) and ACF (3.5.8.1)