if you already gotten to mounting the samba partition...say to /mnt/music_repo
and the old computer supposed to behave as a mp3 player has the username joe.
i use for this same purpose. rhythmbox. for this, i create a bind from the mount point to my music folder.
in fstab add the line
when you start rhythmbox it will find all the music automatically (first do a mount -a)
/mnt/music_repo /home/joe/Music/music_repo bind 0 0
i do a bind instead of mounting directly because i find it more elegant to have all my mounted filesystems inside /mnt and then bind different points to where i need them.
another useful hint, is to add a dynamic playlist based on path. this way you can have your music separated, in local and samba.
hope it helps.