I'd check for water damage before starting any repair. Wind blown rain on a ridge vent?

"Really not sure where to start."

Start by finding out if pop-corn contain's asbestos. If the home was built before 1980 , scrape a tablespoon full into a zip-loc bag for lab testing. Manufacture of drywall products containing asbestos was banned in 1978. Selling products made before 1978 was banned in 1980. If your home is on the borderline,pinch pop-corn kerrnels between fingers. If it is styrofoam like,there is no hazard. If it crumbles to dust,have it tested. If it contains asbestos,consult a reliable drywall company to have repair done. What to do with remainder of house is a discussion for another day. The crack look's to be nothing more than poorly applied tape peeling off. If area isn't water stained,simply removing tape at the seam then retape,texture and paint is all that's reaquired. Walk in the park,ever day job for drywall installer. If drywall sheet has sagged or area is water stained,best have a general contractor address it.