Thanks for sharing. I'm so sorry to hear of your loss. But take comfort in knowing you did the right thing. Ringo needed the peace that only you could give. What you did was the most unselfish act. You are now taking the pain and I'm sure Ringo is up there jumping around on the beach stealing cookies.
Just last year I had to do the same. My path is similar to yours. We saw an ad in the paper as well: "1 yr old red/white Basenji". We had great times hiking and playing on the beach. Brie was just over 14 last year. A year prior she lost her hearing then her bladder control then most cognitive abilities. I started working from home and was able to spend more time with her. But towards the end, she didn't seem to recognize me. She started to walk into things and was rapidly loosing weight. I saw her fall down a flight of stairs and it was tearing me up inside. I talked to several vets who all came to the same conclusion. It was time to let go. It was the only way I could give her her dignity back and it was the hardest decision I've ever had to make. Ever.
It took several weeks to start to move on and several months to not think about it ALL the time. I still think about her a lot, but now I think about the good times with her. Just take some peace in knowing you did the right thing. You had some great times with Ringo. Most dogs never get to go the beach or share experiences that you did. You gave Ringo a great life and I'm sure he's up there driving Brie nuts about now. God has a special place for animals and I truly believe you'll see him again.