You're not gonna find any pre-Colonial South American literature, given the non-existence of writing. Any talk about current Andean folklore is going to be heavily influenced by years of cultural/religious syncretism, so it's hard to recommend any good folk tales or legends (since that's what you seem to be looking for). If you've got no experience in South American archaeology, I would recommend a translation of Guaman Poma's Buen Gonierno y Nueva Coronica. Poma was a local Quechua-speaking fellow whose family manipulated the conquest period political environment to secure a power position for themselves. His book, among many other things, contains a transcribed oral history of the Inca royal line, the closest I can think of to "literature" that might be available to you.

If you can get away from strictly literary sources, I recommend you focus on the change of certain customs peculiar to the Andes and how those changed with Spanish influence: burial customs, ancestor veneration, the ayllu sociopolitical unit, or landscape features venerated as wakas. I can recommend the book Invaders as Ancestors by Peter Gose as an excellent resource about intercultural appropriation and syncretism in the colonial and post-colonial Andes. The chapters are neatly divided by subjects, and it includes a great number of case studies form colonial records/ethnographies (which might be what you want for the "literary" aspect).

Might I ask what kind of assignment or class this is for? That might help to point you in a better direction. Writing about a comparison of one culture before and after conquest is a challenge itself in 10 pages; writing on 3 different cultures might not end well.