Gilchrist smashed nine fours and three sixes in his knock of 118 from 132 balls in front of an adoring home crowd of 17,967.
"It turned out to be a perfect day really," an emotionally-drained Gilchrist said after the match.
"Today was always going to be a big day. I was more nervous about it than any other day leading into here and I'm glad it's done and I'm thrilled with how it's gone. I must admit today that it really hit me that it's all finishing."
"A century in the last game and a win. That was really satisfying given we weren't sure what sort of total we needed to post. It was an interesting wicket. A bit tense there through our bowling period but the guys turned it on when we needed to."
Gilchrist jumped for joy and pumped his fist in the air after reaching his 16th ODI ton. He spent a minute acknowledging all parts of the crowd and soaking up the atmosphere before giving batting partner Michael Hussey a big hug.
"That celebration, it felt like the guys I was batting with, the teammates, were willing me on to that 100," Gilchrist said.
"I wanted to repay them and say thanks to them, and thanks to the crowd, the people of Perth.
I'm saying a lot of thanks around the country but today was a particularly special one ... a lot of emotion in there."
"I felt I was so slow today but Punter sent out that directive and the wicket made for that style of innings. I wanted to start going harder at around 75 or 80 to try and up the tempo, which obviously brings risk, but the message came out to keep going."
Sri Lanka captain Mahela Jayawardene heaped praise on Gilchrist after the match.
"Gilly's had a remarkable career," he said.
"I think Gilly has done international cricket the world of good. He's changed the concept of a wicketkeeper-batsman, especially in Test cricket, and in one-day cricket as well, so credit to him."