The fittings are called Fernco fittings and you will find them at HD.
They are in the plumbing section, usually above the regular pvc
fittings.
If you have a sawzall, Lenox makes a blade especially for cutting cast
iron,works well. I have found that not all cast iron pipe cuts the
same. Some pipe seems to cut easily, others take 10 minutes to cut
thru. Most of the time with a new blade I cut thru 4" pipe in 3 minutes
or less.
mike