Leak in cast iron pipe

Hello all I was under the crawlspace of my house (built in the 30's) and noticed a slow drip from the runoff pipe from the kitchen sink. I then saw the leak get worse and start gushhing when my wife turned the sink on. The leak seems to be right at the bottom of the elbow bend. The elbow also seems to run into a joint leading outside to more CI pipe. Is it possible for me to remove the elbow, put caulking in and replace it? If so is there a specific material I should use for a new elbow piece (CI,PVC). Thank you for any and all help.

if you do not possess the knowledge to cut cast iron with a crescent wrench, or have a set of ratchet cutters handy

i think you need to call a pro. that is not a diy job

Just get youre self a sawsaw.diamont blade.mission bands.abs pipe/fittings ,abs glue.tape measurement.put them together and go crazy down there.its the way i learned..upload some pics for better instructions then these great ones i just gave you.