if there was that much "soap" spilled in the trunk, you may never be able to get it out. plus, there may be issues with mold if it was not taken care of correctly by the previous owner. you should buy a new spare tire cover and floormat to replace the soiled ones. it should run you about $160 plus tax according to the parts database i have access to.
as far as the interior goes, you should get a serious interior detail. in theory, you could try to do it yourself, but it may be worth having everything professionally cleaned. make sure the place you take it actually takes out your seats, so they can clean all the gunk out of the seat tracks and under the seats also. thay may be what doesnt smell so good if the last person had kids. this may set you back a few hundred, but it is worth it when the car doesnt stink afterwards!
as far as the paint goes, i would first try some sort of paint restoration kit from pepboys or kragen or something. claybar, wax, polish, etc. that may spruce up the paint. if the clear coat is peeling, you out of luck, and you may have to repaint.
good luck, and congrats on your purchase. if the car is mechanically sound, thats really all that matters. the rest will come with time.