I was going to suggest the same. My "submarine" 2005 FGT had that slow leak, which resulted in the car just never holding the coolant for very long. I believe I got that fixed (O ring) a week or two before car was submerged...
It's a lot easier to reach the O-rings in conventional front engine cars than in a GT. If you only have to add refrigerant every two years, or even once a year, I would leave the O-rings alone. You may cause more problems by trying to replace them.