He does it either way. On mine, he'll likely just do the work under the cab.
John had the cab off and fluids all drained in right at 2 hours yesterday. He plans to have the heads off, egr system off, and oil cooler off today as well as get the studs in, new gaskets on and the heads sitting on the studs. He's hoping to have it buttoned up tomorrow afternoon and be waiting on the tuner. It should arrive today and I'll be uploading the tunes from Eric at Innovative this evening.
Originally he was going to do the job without pulling the cab, but he found the famed bed plate leak while he was checking it over and decided it would be easier to just pull the cab.