Certainly worth a shot if the water has got inside it could have damaged it, the ring your talking about dosen't need to be changed it reads the transponder in the key, so long as the PATS and the key are paired there will be no problem and of course the ECU is identical.

CPS= Crankshaft position sensor and it won't be near the coil pack, most likely it's mounted near the flywheel (As it uses the ring gear for reference) where as older cars actually had it mounted by the crankshaft pulley itself in either case the it's still measuring the 'crankshaft position'.

Martin