Unless it was EWTN, this variety is best avoided.
I do not think the mainstream Catholic view is that Mary did not experience death, but it might be allowable piety.
I do not think that the doctrine of Immaculate Conception has any consequence to the Orthodox mariology, as it merely shifts the point at which she achieved sinlessness to the moment of her conception, while in the East that point remains undefined, but, from what I hear, is typically thought of as happening at or before her presentation at the temple. I am not the one to ask, -- Jo has the best grasp on the Catholic doctrine this side of the Alps.
Actually, the priest was a pretty good representative of your faith. It was on a Christian television station about 20 years ago, with a sort of panel discussion with a Lutheran, a Baptist, and a Catholic for clergy.
The Catholic pretty much cleaned up, from my perspective (I was a Protestant at the time.) He was calm, had tightly reasoned arguments, etc... He explained what a tradition was for the first time in a way that I could understand it. I was already drawn to the "catholic" world from a liturgical and sacramental standpoint, but had a long way to go in the theology department to accept some of the things I had been taught were wrong as a Protestant. It was a helpful moment for me, even though I would never end up a Catholic.
Anyway, he certainly did not portray the idea that Mary didn't die as the mainstream view, but simply said that there was no consensus within the Catholic church on the question when the then Pope asked Catholic clergy around the world to tell him what they understood the tradition to be. Thus the ambiguous wording of the declaration. As to whether it is allowable piety today, I don't know, but it certainly was allowable piety at some point.
And actually, the Immaculate Conception does have consequences for Orthodox beliefs about the Theotokos.
There are any number of implications, but the main one is that if the Theotokos was born without the effects of the ancestral sin, she would really not be like those of us who are, and wouldn't be an example for us to emulate in the same way that she is in the Orthodox view.
Christ lived a sinless life and we certainly imitate him in every way that we can, but of course he was God, so he had a bit of an advantage in following the command "be ye perfect"! Certainly he was tempted in all ways as we are, and his human nature was like ours in all ways except for sin -- his was a "pre-fall" human nature, unlike ours.
The Theotokos had a post-fall human nature. Her sinlessness was achieved with the same tools at her disposal that we have at ours. Even though she was morally guiltless in her life, she still needed a Savior just as we do -- because of her inheriting the effects of the ancestral sin. Without a Savior, death would hold her captive. She was born with corruption and death and the tendency to sin, just as we are. Her holy life was in no small part the result of the faithfulness of her parents and the piety of her extended family. All of human history led up to the birth and rearing of this one little girl who would be a vessel worthy of bearing the eternal God.
The Catholic view is certainly that she needed a Savior, and that the merits of Christ's sacrifice were applied to her "preveniently." But as to her life, she began it filled with "excess" Grace from the moment of her conception (thus her "extra" grace can be applied to others.)