It would help to know the age of the caravan and how much of the assembly you're wanting to remove. A lot of years ago I had a Sprite Musketeer and to remove the top of the roof vent it was only a matter of undoing a couple of wing nuts, removing the bolts and the top was free. On later caravans with lift and slide roof windows, the attachment is more complicated and probably would be best left alone. To start removing the frame will break the water-tight seal between the frame and the roof, which will need to be made good on reattachment.
hi its a 2008 bailey Bordeaux i have done the little bathroom one ,,was easy,,but there is a big one with what looks like telescopic dampers on but i managed to get with a ladder and get it cleaned ,,thing i will leave the others ,,,
Check this out, it shows how to carry out repairs to the Heki, you could remove the doom for cleaning..
http://www.leisurespares.co.uk/files/repair_heki_2.pdf
I just skim read it but it looks like you need to remove the gas struts then remove the hinge pin to enable doom removal.