Hello Mihai,
This article is pretty close to what you have requested (MP3 instead of WAV). You can sign up and download the software.
http://www.elektor.com/magazines/2011/march/mp3-one-two-three.1706996.lynkx
Other SD Card examples can be found in the Chip Support Library.
http://software-dl.ti.com/dsps/dsps_public_sw/dsps_swops_houston/C55X/latest/index_FDS.html
Hope this helps,
Mark