Hi lightfantastic, a while ago I removed the headliner, because I wanted to add sound deadening to the roof. I got the headliner cleaned in the process. It was actually easier to get it in than out. It was hard at first to figure out the method, but what I did was removed the headrest from both front seats, then have them reclined all the way. I got it from the rear passenger's door so I also lowered the driver's window to have all the room I could get. You might bend it a bit in the process, but don't worry (I bended and broke it a bit in the rear middle) if it happens you still have the pegs to support it. My advise, be careful and patient and once you have it inside and ready to install, start from the sides to get it square in order to avoid it from bending when totally installed.
All the best