Its a big hassle. I would only recommend a professional shop do it because of the mess you can make out of it. There's a cardboard backing that comes out and the material is attached to that, then manuevered back into the cabin of the car and reattached. All the trim has to come out, the visors, and working around the sunroof, a major pain in the butt. Down here in south Florida it usually runs about $200 to do the job, well worth it.
Installing headliner
Mike