Certainly do believe in Our Lady of Guadalupe!! The tilma was made from a very rough fiber made from the agave cactus. It generally falls apart in 5 years. One which was made and protected under glass (which the tilma of Our Lady was not for a great many years), fell apart & rotted after 10 years. There is no paint on the original image. As for her looking like an Aztec Indian, of course she did! She was talking to Juan Diego, who was an Aztec Indian in his own language. By appearing in the clothing of an Aztec of high rank, with the symbols of an Aztec of the ruling class (stars on the covering, the light cloth of her gown, the black/dark ribbon at her waist (which indicated pregnancy in their culture) and her hair down (which indicated virginity) she was a great sign to the Indians who saw the image. Also, in 1531, the winter solstice actually fell on Dec. 12th, which was a day that was important to the Aztecs.
That is why so many converted after the image was seen by them. They knew she was one of them, and had said she was their Mother, and they accepted both her and her Son based on this image. How wonderful that she can bring her Son to even the pagans just by showing that she loves them as a Mother!