This article is from the Feline Leukemia (Cats) FAQ, posted to rec.pets.cats newsgroup. Maintained by Erin Miller with numerous contributions by others.
Well, your own grief issues aside, from a medical point of view you do not need to wait very long. The virus is fragile outside the host, and I know of one vet who has even stated that it would be safe the next day. Personally, I would wait a week at least. You should definitely discard the litter box and food/water bowls, or else clean both well with household detergents or a 1:32 bleach solution.