The Swans prevented the Black Cats from ending their season with five successive Premier League wins, with two quick-fire goals from Nathan Dyer and Marvin Emnes effectively ending the game after 14 minutes.
Although Fabio Borini got one back for the hosts, Wilfried Bony notched his 16th league goal of the season to complete the scoring.
"I should probably retire at the end of the season now that I'm permanent manager," Monk jokingly told Sky Sports. "It was good to end on a positive note and I thought the boys delivered a very good performance.
"We spoke about it in the week, making sure we ended the season on a positive. We had something to play for in securing the 12th place, and we managed to do that.
"All in all, with the season that we've had - Europa League, the Premier League, the change of manager and everything that has gone into it, to finish five points behind out best ever total since we've been in the Premier League, I think it's been a very good season.
"It's been great for me this past three months as a learning process and a taste of what is come.
"From next season, I will be judged more harshly on my own merits - I know that, I accept that and I'm not worried about that. I'm just looking forward to it, being judged and doubted. There's nothing better than trying to prove people wrong."
Monk added it's vitally important that striker Wilfred Bony remains at the club next season, saying: "We're lucky that we're in a position that we don't have to sell anyone.
"It's up to us, and Bony is one that we will be keeping. He's one that we want here and one that has improved massively with us.
"I think there is an even better player that what we've seen this year. Him and a number of others, I think you will see better players next season."