Dont be scared of a locker, they are not as nasty as people make them out to be, my diff stuffed up in my old rx7 and a mate locked it, i was too scared to drive it at first (it was raining the day we welded it) because of everything they were saying about a locked diff, but once i drove it i realised its not as bad as people make them out to be, only really notice it on tight round abouts u turns and parking, even then there very manageable, and one your having fun they are very predictable, will always do the same thing at the same point.
Dont know what a spool is worth but if its only $50 then its worth getting one to try it, if you dont like it put it in the for sale thread and get your money back.