I recently bought a headliner and sought out an installer. The guy said "no problem - couple of hours" - as he had 20 years of experience in the restoration business, and had done scores of headliners on import and domestic cars. Today he put it in my project 544, The windshield and rear glass was still out of the cars.
Eight hours later he had done a barely passable job, and admitted he had never before put one in a vintage Volvo- and would never attempt to do so again.
Would I try this myself? You gotta be kidding!