Hi Mel!
I am 24, but I got my navel pierced at age 16. I begged my mom and she finally agreed and took me. I went to a respected studio, asked all kinds of questions, then picked out a 24k(?) hoop - they only pierced with hoops then. It hurt mildly, although I have a higher pain threshold. But, pain is a pretty relative term right?
I agree with earlier posts that with a few guidelines in place, it should work out just fine for you. No cheap jewelery (especially if you have allergies to metal.) Take very good care of it as far as cleaning it, soaking it, and not "picking at it". And be careful with it. I nurtured mine until it healed, took it out 5 years later while I was pregnant (had no scar), and put it back in after I had my son. It's in my belly as I type and my husband still likes it!
Good luck! Next is tattoo shopping right?