1. The visors mount in the same manner with phillips screws (both lighted or non lighted) wires go through the hinge
2. You do not need to remove the headliner you can get it down far enough by removing the A pillar trim from both sides, removing the visors/clips, and center overhead console. To remove the entire headliner is a much bigger job, in addition to what already has to be removed the rear seat has to come out to remove the C pillar trim, trim moldings above each door, dry cleaning hooks from each side, and a few plastic push retainers (which usually result in deformed headliner in the adjacent areas from removal)
3. Mirror mount is the same
Most recommend to replace the at least the Heater Core (try and find a copper one if possible) as the dash removal is a process. To get to the evaporator core is a deeper process which adds a few hours to an otherwise lengthy process.
Others may disagree, but in my experience to properly replace the upper dash pad the entire dash must be removed from the truck as there are around 17 screws which retain the HVAC ducts that are only accessible from the back, some you can reach with the dash partially removed but a few cannot be. There are a few good write ups on dash removal.