I don't have a Sanibel but I do have a Dometic ducted A/C unit. There is a black plastic screw on the end of the filter housing. Just turn it counter-clockwise with a flat screwdriver and the housing will come off and then remove your filter. Hope this helps
foam filters are a waste of time. they filter essentially nothing. if you really are concerned, then get a small HEPA filter at walmart. i leave my foam out to improve the airflo and reduce freezing up
Mine had a lot of "nothing" on them that I washed off when I cleaned them.