Until the mission editor gets a fix, I would advise only playing these working missions:
http://bbs.hitechcreations.com/smf/index.php/topic,287915.msg3652965.html#msg3652965This mission, Attrition, will crash at the warp point until we get a fix.
As for a soundpack install, you download the pack, unzip it & then place this new Sounds folder into your AHII folder, replacing the default empty Sounds folder, too easy.
Sniff, as for the skin, where did you download it, did you unzip it if necessary & where in the game folders did you put it? It needs to be in your AHII/Skins folder.