a) the leak could be all of those things...what i suggest is strip the trunk and see where you can find it coming in from...if you can

b) to take off all those panels....get a small flathead screwdriver...pop off all those little black clips *if its a pin...push it in then use the screwdriver to pop it off*....do the same for all of them...i believe there is about 14 and a couple will crack but as long as u still have the majority of em u wont notice later. i think there might be a 12mm bolt inside of holes right in front of where the antenna is just behind where the seat rests....it's not a fun job to pull those things off considering it's 3 very large pieces...

once you've done that try to trace the water leak ....does it smell like anything? besides mold.

thats about all i can think of at the moment...but im tired...lemme know how it goes and i hope this helped a bit