No. I do not think that the ordeal with Zaroff changes Rainsford's mind about hunting. I think he still enjoys hunting. I think he still is fairly cold. And I still think he finds hunting humans distasteful.
Rainsford is a world renowned hunter. I don't think his ordeal changes anything, especially knowing that he slept quite soundly after killing Zaroff. Early in the story the reader is introduced to the fact that Rainsford is good at hunting and has little sympathy for his prey.
“…We should have some good hunting up the Amazon. Great sport, hunting."
Rainsford: "The best sport in the world."
"For the hunter," amended Whitney. "Not for the jaguar."
"Bah! They've no understanding."
"Even so, I rather think they understand one thing--fear. The fear of pain and the fear of death."
Rainsford doesn't even believe that the animals he hunts have fear. They have no understanding of what is happening. I think Zaroff feels the same way, which is why he enjoys hunting the only animal that can reason -- humans. Rainsford is appalled and intrigued all at the same time, but ultimately doesn't agree to hunt a human. The downside of that decision is that he becomes the hunted.
I've read an analysis or two that say Rainsford enjoyed killing Zaroff and is likely to begin and enjoy hunting humans too. Basically Rainsford will continue Zaroff's sadistic tendencies, and that's why Rainsford slept so well. I disagree. I think Rainsford slept so well because he knew that his life was no longer in danger. He killed Zaroff out of self defense, and he can now finally relax after his three days of not doing much sleeping. It's even conceivably possible that Rainsford has become even more immune to any feelings that his prey might have and that's why he slept great. It's my guess that he goes back to hunting with an even cooler/colder attitude toward his prey than before.