My dad is 96 and was recently diagnosed with colon cancer. Shoud the surgery be done?

Its hard to say if it should or shouldn't. Most depends on his health in general. And you really need to look at the whole picture, will this really help him or just make what time he has left on this earth miserable. The surgery alone could end his life because of his age and any health problems. Go and get more then one opinion from specialists, and most of all what dose dad want? If he don't want to then let it be, but if he dose make sure you know all the out comes from this. Only then can you really make a good decision to go forward or to just make what ever time he has here as happy and comfortable as possible. God bless you and your dad and your family