Enlightenment in Buddhism happens over several stages, and different traditions use slightly different maps and names/numbers for them.
The first stage of enlightenment is called stream entry in the early Buddhist texts, and the first bodhisattva bhumi in Mahayana-Buddhism. All schools seem to agree that it involves supramundane insight into to how the five aggregates that make up human experience lack self/substance, in addition to highly developed moral conduct in thought and deed, no doubt about the right way to practice and finally, a lack of exaggerated belief in the efficacy of rites and rituals.
So, enlightenment is not primarily an experience in Buddhism, but a milestone along the path. A point of no return, where a person has been transformed to the extent that the final stage of enlightenment has become inevitable.
If what we call stream entry / first Bodhisattva Bhumi should happen to a Catholic, it would impact that person’s belief in God. The view of God as unchanging, self-existing, utterly simple and yet cause of a multiplicity of effects would not be compatible with the insight they would have had, but versions of theism such as
Process Theology would still be viable. Nor would it be acceptable to kill insects or animals, or use them for experiments, as the Catechism of the Catholic Church allows, and all the violence the OT attributes to God would have to be firmly rejected. Views about how the eucharist is transformed into the body and blood of Christ would have to change, or simply be left as a mystery as it is in Eastern Orthodoxy. Theories of atonement would radically change, etc.
This is just off the top of my head. I am not sure it is actually possible to remain a believing Catholic after such a transformation. Certainly not an orthodox Catholic.
