How badly is the outer skirt damaged - a few strands missing or totally shredded? If it still runs well, it'll probably still get bites.
Re skirting - P.B.W (high priest of moldcraft) is on record as saying "I only ever use a single skirt on Mold Craft lures. When too many dingle dangles are cut off cut them all off and glue the inside skirt in place."
I can say though - the fit of the inner skirt in the Standard size wide range is pretty poor, at least on the example I purchased in Florida. The inner skirt of the Senior size fits much better.
In any event, they're cheap enough (in the States anyway) that if the head/outer skirt combo gets too badly damaged you can just trash the lure and put out a new one. Save the head for me if you would - I'd rather like to mold a "hard head"...