The uproarious comedy Cedar Rapids comes from the blushing cinema of embarrassment that gave us Cyrus and The 40 Year Old Virgin. At the film’s center: a 34-year-old sunny geek Tim Lippe (Ed Helms) convinced selling insurance is an expression of god’s love. As heartily as he sells that message, you almost begin to believe it. You don’t know whether to hug him or give him a wedgie.

Is Lippe arrested? Baby-fied? Filmmaker Miguel Arteta (Chuck & Buck, The Good Girl) doesn’t make any bones about the stunted but poignant status of its orphan hero, who has lost both parents and looks to his boss for nurturing. Lippe even has a Mrs. Robinson, the over-age hottie Macy Vaderhei (Sigourney Weaver) who, wait for it — used to be his seventh-grade teacher. Can you say mommy complex? That relationship pretty much sums up the kinky and sweet rhythm that Cedar Rapids grooves to, a film that makes everything from adultery to snorting coke look positively peachy-keen. Should you laugh? Should you cringe? Should you hide your eyes behind your hands?

In nerd cinema, every geek has his mountain to scale, his churning river to ford, the leaky ink pen in his pocket. Seems the insurance agency’s star-seller has just met with an unfortunate end via auto-erotic asphyxiation. So it looks like Lippe is up to bat. Lippe’s crucible is his company’s annual insurance convention that his blowhard boss Bill (Stephen Root) packs him off to with strict orders to come home with the coveted lucite Two Diamonds Award, the Grammy of Midwestern life insurance. He leaves his beige world of Brown Valley, Wis. for the phantasmagoric Oz of Cedar Rapids, Iowa, with its decadent trifecta of hookers, hotel bars and indoor swimming pools. Giddy at the thrill of flying on an airplane for the first time and interfacing with the big, bad metropolis of Cedar Rapids, Lippe straps himself in for an adventure of scavenger hunts and business-card hand-off cocktail mixers, with regular calls back to his sugar mama Macy for moral courage.

The title of the film is a joke about the places we consider cesspools, not New York or L.A. in this case, but a seemingly white-bread bland town that, it turns out, is in fact a teeming sewer of vice and corruption. And that’s within the walls of the convention hotel. There are early signs that all is not right in Dodge. A fresh-faced hooker trolls the convention lobby looking for a date and the convention custom — despite the lip service paid to the insurance company’s born-again founder — appears to be booze guzzling and bed-hopping. Worse still, Lippe has been housed in the same hotel room with his agency’s arch enemy, the client-stealing scumbag his boss has warned him away from, Dean Ziegler (John C. Reilly).

Cedar Rapids’ babe in the woods set-up is hilarious. Lippe is all nervous-nellie about forking over his credit card for the room deposit and carries his traveler’s checks in a zippered money bag strapped to his body. He expresses white-boy shock that his other roommate is a b-b-b-b-b-lack man, possibly the first he’s encountered in the vanilla ranks of Iowa. It’s all just too-too awkward and unfamiliar for poor Lippe, whose first encounter with insurance poobah Orin Helgesson (Kurtwood Smith), the man who has the ability to bequeath the Two Diamonds upon him, in the hotel’s gym locker room is a certifiable spit-take.

Like Belushi or Jack Black, John Reilly’s comic mojo in Cedar Rapids is pure id: Ziegler is an uncontrolled mess of crude jokes and inappropriate bon mots who suddenly snaps into morose when reflecting on his ex. His straight man is the equally-ribald-in-his-own-way Ronald Wilkes (Isiah Whitlock Jr.), whose infomercial-perfect diction, starched suits, and affable business-ready manner carries a whiff of sadness; he’s a black guy in a white world who’s done everything he can to fit in. One of the most subversive black characters in movies in a while, Whitlock is so square he gets his ideas of gangsta where we all do: from TV, specifically the HBO series The Wire (which he starred in as the slimy Clay Davis). Whitlock’s performance is pitch-perfect.

Rounding out their happy quartet is the family gal Joan Ostrowski-Fox (Anne Heche) who uses the convention every year as an opportunity to forget she’s tied down. Again, there’s that whiff of sadness behind the comedy. They take Lippe on as their prodigy, introducing him to the pleasures of drink (his guzzle of choice: sherry) and loose women (he falls hard). As Lippe, Ed Helms retains his shiny innocence even in the midst of Midwestern depravity; he somehow manages to convince, and endear, a shiny, gullible Jimmy Stewart trapped in the flesh-pot of Hooverville.

Cedar Rapids gains points for mixing up its very, very rude comedy with a real sense of purpose. It reveals the ethical handicaps and general bad behavior in a supposedly god-fearing white collar world and the honor-among-renegades of Lippe and his crew. You end up rooting for the geeks and for the corny but reassuring message that friendship and stand-up guy (and gal) values triumph in the end.