I am a cis-woman, and my bf is FtM. We had a non-sexual relationship for almost two years. He felt worried about me refusing him. When I knew he was FtM, I have to recognize I felt anxious, because I had never known about trans people. But I love him and finally it was effortless to accept him exactly as he is.
We are starting to feel comfortable with our nakedness. By now, we always use a prosthesis but it is more because of his shyness than because of me.
I think the only important item you have to measure in your relationship is if he loves you. If he do, soon or later, you will learn to pleasure each other.