ok ive done alot of remodeling. is it a multi story house? is your closet bottom floor middle top? is their an attic or a crawl space?
as to your walls, plaster that old should be white probly semi powdery by now and easily crumblable between fingers. or if its been remodeled it could be cement board which ive seen people use to even out plaster and help the new stuff stick, could also be fireboard, fireboard that old will be concrete and asbestos so dont breath the dust
oh yeah, lath and plaster (usually horsehair plaster) will kill your drill bits, either draw a circle and chisel the plaster away (a flathead screwdriver works fine for this) then drill, or buy super cheap bits
if your on the top floor make a hole in the cieling just big enough to fit your finger through. then feel around poke a stick see how much room you think their is, if its clear cut a 3-4 inch hole, and vent.
if your on a middle floor, your kinda screwed. just vent heat to the room and make an ozone generator, T5 12inch Florescent fixture 16-24$ T5 12inch UV bulb 6-20$
venting into your wall is a bad idea.to start with if the cavity is sealed the fan will pressurize it slightly causing air resistance, this will cause back preassure on your fan, which will make is more noisy, and sometimes it can fry the bearings because of their inability to deal with lateral thrust, and if moisture gets behind that plaster it will be very very bad (im talking full on mold infestations and RAPID plaster decay). if its not plaster you can vent into the wall, PROVIDING that space between studs runs entirely unobstructed either to your attic or your basement, this mean no fireblocks no insulation etc.
then go into your attic or basement and cut another hole DOWN into the wall, between the same set of studs (you remebered to measure right?
you most likely will not be able to make even a 3 or 4 inch hole so i would suggest a series of 1-1 1/2 inch holes (also if its near an outside edge drilling down will be almost impossible without a right angle drill, so you have to drill at an angle). if you dont know where to drill heres the cheaters way, take a long 1/8th drill bit, drill as close to the wall as you can STRAIGHT up into the attic measure then distance from wall to hole and write that down, then shove a peice of brightly colored wire through the hole go into the attic and find your wire, now that you know where the edge of the wall is, just measure, lath+plaster 1/2-3/4 thick house from 53 might actually have studs 4 inches deep, measure to make sure, then make your holes. heat rises so the attic is better than the basement, in the attic convection combined with the venturi effect will help draw the heat up
if your on the bottom floor vent down a house from 53 probly does not have a concrete slab so there should already be alot of moist dark air down there. but crawlspace venting keeps any smells kinda localized to your house. so again youll need an ozone generator down there (on the upside the ozone will kill the mold and mildew in your crawlspace
ok that should be enough for now