I've got to agree with fitting it outside the tank. When I changed mine the faffing around trying to get all the gubbins out then back into the tank in one piece was truly frustrating. After fitting the new filter and putting it all back together my fuel gauge wasn't reading accurately so I had to do take it all to bits again!
Smoking lots of fags and removing fuel tanks is not sensible but is completely justified in this mother of all frustrating jobs!