Echoing the hands off approach that other posts have advocated. I don't know exactly what your relationship with your father is like, but I, personally, would not feel comfortable proselytizing to either of my folks. Respect his decision, offer your thoughts when solicited, pray, and be a living witness. I think those are the most "Christian" things you can do in a situation like this.
I, for one, would be overjoyed if my protestant father were considering Roman Catholicism. As it is, neither of my parents are religious and may never be, at least in the outward sense. Not all paths lead to Christ, but that doesn't stop Him from walking on them to find us. That said, I definitely believe that the Roman Catholic Church leads people to Christ, and I would dare venture to say that there is a "fullness" in Rome that is lacking in Protestant groups. Of course, the ultimate fullness, I believe, comes from our Holy Orthodox Church. But I'm certain that no amount of reading or arguments will convince someone of that.