Coumadin is fine. The same precautions would apply to you as it would anyone else.
The one exception is possibly vitamin K. It is possible that you would have less vitamin K than those with a colon, since much of what we get is made by bacteria in the colon. They tell you to not eat too many foods rich in vitamin K (like broccoli) or at least eat it in regular quantities, because it can interfere with your clotting times. But, I never found it to be a big issue for me. I was on it for about six months.
As to the ileus, sure, it is possible that the spinal had an effect, but a general would have the same effect, if not more. Plus, all the opiates you will need have an additive effect (unless they are using local anesthetic infusion for you). Don't know if they use that for hip replacement.
Jan