I've had the fuel rail off in the past and was planning to replace all the o-rings on the fuel injectors.

The top o-ring is easy. But the bottom one has a plastic ring that protects it. After breaking the first ring I decided there was no way to replace the bottom o-rings and I just used silicone to freshen up the rubber of the o-ring.

Is there a trick to removing and replacing the bottom o-ring without breaking the plastic protector ring?

I always cut them and the replacement fits back over the plastic retainer.