Hi,
Tackled this job myself a few years back and can offer..
Lid - I used 4" polywhatsis, just put it on top on tank, it sticks a foot out all around, end of story
Light, put in TWO lights as the attic is high on the shadow factor and you do not want to lose your footing, so a bulb at either end of the attic to avoid the shadows as much as possible
Laying the insulation - didn't bother taking up old stuff, put on ole clothes and simply threw them out when finished because the glass fibre gets everywhere
Tip, cut a large square bit of timer to avoid balancing on the joists, easy to pick up and move around with you, also dont insulate near the eaves, and to finish rolling the insulation I used a kitchen brush to reach into the ever narrowing space as the roof meets the eave.
Cut the insulation in the attic itself.
Top quality eye/mouth face protection required.