17 years PO, I think one implant is leaking. What should I do?

If your saline implant is leaking you will get a "flat tire" and it wont be hard to tell. If your breast deflates go see a board certified plastic surgeon and inquire about replacement. Your only decisions are do you want to change size and do you want a silicone or saline.

Fortunately, saline implant rupture is not medically dangerous.  You should consult with a Plastic Surgeon in your area to discuss removal and replacement.  It is typically a short outpatient procedure.  Best wishes.

You just need to set up a consultation with a reputable surgeon in your local area. Replacement of your implants can be a very straightforward procedure, often with little downtime. Most implants have a warranty for rupture and it is likely that you will not have to pay for the implants to be replaced. I would suggest replacing both of the implants.