As far as replying to your friend, I would start with this apparently Mormon site that reviews archeological claims regarding Mormonism.
http://www.bmaf.org/articles/review_ain ... __andersen
"I do not agree, however, that he “provides compelling evidence for the location of the cities of Bountiful, Zarahemla, and Moroni,” and Lehi. I think it is, at least, disingenuous, when he continues to push documents as authentic that have been determined to not be authentic, without further testing to prove or disprove the authenticity of said documents.
Ainsworth proposes the authenticity of 12 small gold plates, known as the Padilla Gold Plates, “found” by Dr. Padilla in late 1950’s in Mexico. Ainsworth apparently agrees with Jose Davila that “Jose knew the value of the five gold plates—which he believed to be authentic--to the Book of Mormon. His stated goal was to present them to the LDS church as evidence for that book (page 19)”. Ainsworth believes these plates contain Reformed Egyptian characters of ancient origin (page 268). All twelve of these gold plates have been examined by competent qualified specialists and determined not to be authentic as claimed. "
"There is but one straight course, and that is to seek truth and pursue it steadily."
"Truth will ultimately prevail where there is pains to bring it to light."
George Washington