Yet, I see that some Mormons claim to believe in evolution. How is it possible to square evolution with Mormon doctrine?
By realizing that when scriptures say God created man, it doesn't say how. Dust of the earth? An excellent metaphor for evolution.
Doesn't the fact that evolution is in reality the way humans came to be spell trouble for a religion which teaches God has a body
How so? God (a human from a planet where humans evolved from lower life forms) created a world wherein the same principles governing evolution exist and by it brought forth physical human bodies.
and also claims that God Himself gave Joseph Smith the eternal truths which were to be taught in the temple?
There is nothing in the temple that precludes evolution. At worst, it is simply the scriptural account with some visual details filled in that have not been established by scripture or modern revelation.
Perhaps some Mormons believe the Bible to be errant in many ways, but do they believe what is taught in the temple to be errant, also?
As an LDS person, I believe all LDS scripture and doctrine.
Not literal, perhaps?
Perhaps. For example, the word 'day' in Genesis can mean 'an epoch of time'. And I do not believe that God literally scooped His hands in the ground and made a man out of dirt or clay.
For those Mormons who believe in evolution, do you think God gave Joseph Smith incorrect information about how the earth and all it's inhabitants were formed?
No. But it is possible that God did not give Joseph Smith all the information needed to know exactly what happened and it's possible that Joseph Smith filled in the missing details with what was believed and thought gernally at the time. Besides, LDS doctrine is not defined by what this or that prophet said, it is defined by what the First Presidency and the Council of the Twelve agree to be published.