I would say that RAI is recommended a good majority of the time, regardless of lymph node involvement. Some research suggests that it isn't always necessary early-stage cancers. However, by doing the RAI, I have read and my doctors have said that the follow-up blood tests that check for re-recurrence are more accurate and they don't have to be as concerned about keeping the TSH as heavily suppressed for as long after surgery.
Also, with the RAI, they do a scan to see if there is any thyroid tissue anywhere else in your body (because it will light up like a Christmas tree), so there's that, too. They'll probably do one after the RAI ablation treatment, as well, just to see that everything is gone. Then you'll probably never have to worry about it again.
I got some of the information about the low iodine diet from the nuclear medicine department at the hospital where they gave me the RAI. It's not something that can be done in the doctor's office because they can't keep that kind of thing lying around. So I went in a few weeks before for my consultation with the nuclear medicine doctor, so I could have time to prepare. Then on the day of, I went in, swallowed the pill and went home to my Fortress of Solitude for three days.
I think that if the cancer is a type that spreads to the lymph nodes (which papillary is), that it generally stays in the area, at least at first. In more advanced stages, it can spread further, but that doesn't at all sound likely in your case with such a small nodule. And even if a couple of cells are missed in the lymph nodes, that is what the RAI is for. It targets thyroid cells, cancerous or not and kills them, anywhere in the body. That is why you have to be isolated--should some of the RAI in your sweat or saliva or whatever contaminate someone else, it could damage their thyroid gland (not totally in what would be a small dose, but still not good). I didn't even want to be around my sweet kitty because I didn't want to contaminate her. After a few days, it's all out of your system and you can return to normal.
There are stages of thyroid cancer, but often it's not as much of a focus as it is with other cancers, it seems. I think there are guidelines based on how large the nodule is and if it's spread and how extensively. But if it's in the early stage, especially less than a centimeter, it's not really a concern. Plus, papillary has a great cure rate, especially when it's small.
I recommend writing down all your questions you still have for your doctor and taking them to your appointment. Also, the board is always here to help, too. Best of luck.