This is copied from a text file included in every P:M download in the songs folder:
The list of songs replaced in Project M Demo 2 is as follows:
A01 - Ground Theme (SMB) -> Metal Mario (Super Smash Bros.)
A17 - Mario Bros. -> Fountain of Dreams (Melee)
B09 - 25m BGM -> Kongo Jungle (Super Smash Bros.)
C18 - The Hidden Village -> Hyrule Castle (Super Smash Bros.)
H06 - Victory Road -> Saffron City (Super Smash Bros.)
K07 - Porky's Theme -> Fourside (Melee)
R03 - Hanenbow Ambience -> Ballad of the Goddess (Skyward Sword)
W07 - Green Greens (Melee) -> Gourmet Race (Super Smash Bros.)
W15 - Super Mario Bros. 3 (Melee) -> Yoshi's Story (Melee)
And for your other question, Brawl box allows you to make your own brstms; however, it isn't as simple as turning common music files into brstm's as common music files don't have loop points. I believe Brawlbox needs .wav files, so you will also want a program that can convert any other type of file into a .wav. There are programs with the sole function of converting, but there is also audacity (all of which are free). What makes audacity useful is that you can tweak the equalization as well as see the general "shape" of the song, which will help later when you try to set a loop point in brawlbox.
But let's say that you have a .wav file. Open brawlbox, then follow this chain: file->new->brstm audio stream. It will then ask you what file you want to open (select your desired .wav file). It will then allow you to play the song in brawl box, and set two points in the song where you want the song to loop. This last step may take a long time, as you will be playing the song over and over to make sure the loop is seamless.
Anyways, I highly suggest exploring the brawl workshop boards. The earliest brawl hacking threads can be found there , along with all of tutorials and lists (such as Darksamus') you might desire in the future.
Happy hacking and welcome to the smashboards.
