Good question. Just to play the devil's advocate here, I wonder if it might be good to take a Christian name for one's first name, but keep "Muhammad" as a middle name, to demonstrate that someone can, indeed, convert from Islam to Catholicism.
The name "Muhammad" merely means "praiseworthy" in Arabic, just as "Bara(c)k" means "blessed" --- "Mubarak" is a common Arab name, even among Christians --- and "Hussein" simply means "beautiful". You will see this name among Arab-Americans rendered as "Hassen", "Husson", "Husain", "Hassan", and so on. There is nothing intrinsically wrong with any of these names.