If you want to change your sp theme open mugen.cfg in text editor/note pad then look for the (motif = dir of the system.def)
And as for the lifebar open the system.def that is assigned in the motif then change its fight.def but be sure to check where its located.
For ex. If your lirebars is in another folder be sure to include the folders name( fight = newlb/fight.def) where newlb is the folder name.
But you ignore any of it if you just put your lb in the same folder as your system.def that is assigned in your motif.
And for your sound problem you must be editing the wrong system.def for it not to be playing in your sp.
Arklegend Zinesis's post in HELP! NEW TO MUGEN! was marked as the answer