Yikes, I hate to scare you away from it. If I can give you a large overview, Monahan goes to great lengths to prove that Mahler more-or-less used Sonata form principles in his symphonies up to the 7th symphony. He also believes it exits in the 8th. When I fully absorb what he has to say about the 7th, I'll post here again.
What's also interesting to me, is that both Bernstein and Monahan have pointed out that Mahler frequently uses the Phrygian mode, which is the minor mode that is often associated with the sound of Spanish music: bullfight music, Boleros, etc. As with many of the less traditional modes, you can impose both major and minor chords within that framework.
https://www.youtube.com/watch?v=8tkVz3GhxeIAlso, for anyone who likes to plunk-out short score reductions of Mahler symphonies on the piano, Monahan's look really good and thorough to me. Go to the website above, and then go to "References".