If you still keep in touch with him, why not?
All depends on the relation with your former priest/pastor and also his attitude to Orthodoxy.
My former priest, Roman Catholic, is also my very good friend to this day and, what's more, he has some Orthodox Christians in his family, so I had been talking with him about my potential conversion into Orthodoxy even a few year before it and never had told me "Don't do this", only "I don't know, what's better for you. Bot you can't live in kind of schizophrenia, by practising in 2 churches" (he rather couldn't say directly to me "Convert!", so he said it between the lines), and when I finally decided, in some way he was relieved.
But I've heard also some stories, that former priests were dissuading from conversion into Orthodoxy or even made fuss