what happened to them? did you find the bee's near the food source or the other end? in a clump? any dead brood? bee's head first in the cells? etc
try to determine if it was disease or cold or starvation!
if its not disease I'd just throw them in
most especially if the equipment is older, or if their is no explanation for the hives demise then you might have some concern for disease.
some of the more prominent diseases (at this particular time) can be at least partially remedied by airing out the frames and exposing the equipment to UV (sunlight). some folks who have concerns about nosema c are going one step further and spraying the equipment down with acid and/or bleach as a precaution. a low energy nuclear reactor would certainly be handy to really do a through job in dealing with a host of disease vectors in the equipment. sadly I don't have one of those for you to borrow.
I would use up any existing frames before I added anything new.
Yes, they will clean it up and use the honey. I like to save them as much work as possible by cleaning out the dead bees as best i can and trash on the bottomboard. I mix a cap full (about a table spoon full ) of bleach to a gallon of water and use a hand spray bottle and spray each frame.The hive body and supers i use a propane torch and melt the wax on the frame rest,sides, and corners. This has to get rid of some things and it makes me feel better. :thumbsup: Jack