Sullivan and co-owner David Gold sold the West Midlands club to Hong Kong businessman Yeung for £81.5million after 16 years in charge. A bitter war of words and a High Court battle followed.
But Sullivan is adamant that is all in the past and believes Yeung and his right-hand man, Peter Pannu, have done a good job at City.
Sullivan told the Birmingham Mail: "I hate confrontation and things have now run their course and there are no problems.
"Peter Pannu was doing his best for Carson Yeung and I respect him for that. In fact, I have huge respect for Carson and Peter.
"It was business, one professional against another. Nothing really bad was said and, from the bottom of my heart, I have admiration for them.
"Peter has done a marvellous job. You have to say 'well done to them'."
Sullivan added: "When we sold Birmingham, we sold to someone we felt had the club's best interests at heart.
"What Carson Yeung has done so far, he deserves credit for that.
"The team had an exceptional season, he invested money on players and has not put Birmingham City at risk.
"The spine of a good team was there and Carson has spent money on it and improved it yet again.
"He seems to have a long-term plan and, to those people who are wary because he's Chinese and there's still some mystery, I would say when we took over, we were outsiders and no one knew us."
Sullivan admitted: "I am looking forward to coming back to Birmingham and meeting the Chinese and, when they visit us, we will roll out the red carpet.
"We all knew that it needed a change. The supporters wanted it. Our time was up. We had outstayed our welcome.
"But I'd like to think, when they look back in the years to come, they will accept we didn't do a bad job. It could have been better but it still wasn't bad.
"I don't know what reception we will get tomorrow and I suppose there are always one or two lunatics who will give you grief.
"I'm nervous but looking forward to returning as well."