Hi Christina,
SurfVol is created by SUMA_Make_Spec_FS
ExpVol is any anatomical volume in alignment with whatever volumes you want to map onto the surfaces.
You do not have to have the data under a particular directory structure. That is simply the structure of the tutorials. I don't think you'll need to change nii volumes to BRIK volumes for the purposes of mapping the volumes to the surfaces. You might need to make a BRIK version of the nii volumes for the purposes of SUMA_AlignToExperiment.
@SUMA_AlignToExperiment is a script that creates a new version of SurfVol that is in alignment with ExpVol and your other 'functional' volumes.
By the way, what tutorials did you use?
cheers,
-ziad