It has to be said right off the bat that the first season is a very different thing than the second and third, the third being the darkest but also most powerful. Also, while alcohol use is abundant it is in no way glorified and the viewer is made to feel sorry for the characters reliant on it (especially Orel's father). The sexual element is not graphic, and exists largely as a means to talk about repression of human nature, and of course that sexual repression's effect on the citizens of Moralton (again, most especially Orel's father, who serves as the secondary main character.)
Orel lives in a town of good moral protestants, or so they would have you think. In reality they are for the most part depraved hypocrites. Religion in the show serves as a means of deceiving themselves and others into believing they are good and happy people. Orel himself is a good person, and as a devout Christian, tries his hardest to please God. His comical failings stem from a combination of him being boundlessly naive and having very poor guidance. While the show does have a hostile attitude towards religion it doesn't attempt to show that religion makes people bad, only that it does not make them good and that a lot of bad can come of even completely earnest attempts at doing good under its guidance. As a student of philosophy, I take the show to be a very strong critique of a very popular moral theory, divine commandment (though I feel it can be extrapolated to other rule based theories).
Aside from the religious aspect that so rules the earlier parts of the show, the citizens of Moralton are all explored in some depth, dealing with the issues they seek to cover up. These issues are not exclusive to the religious, they are very real human situations that arise from social pressure, formative experiences, and basic human emotions.
It's a show for adults and kids a bit older. 13 can handle the "bad stuff", but maybe not get the messages. The older the viewer, the more it is likely to resonate with them. The younger the viewer, the more useful the show could be. It's claymation, but it's not a happy show. It has some uplifting moments, but they are outnumbered by depressing ones, which is not at all to say that the show isn't also very funny.
Watch it if you want something that will make you think, not if you want a carefree laugh, a positive role model, and positive messages. As for religious viewers, some of the humor may offend you, as religion is the sort of thing people are quick to take offense about. To my recollection God or Jesus are never made fun of, only people and dogma. If you can watch with an open mind you might have a few laughs and maybe find yourself having a long think about something you otherwise might not.