Depends on the clutch mechanism. A small amount of space is needed between the thrust race and the pressure plate, otherwise the race wears.
It's one of those things you could get away without having for years, yet another supposedly identical car will wear things out. I'd not omit it, you have the bit and it's not that hard a job to change.
While I can't offer any tips for changing the spring, I certainly have done it over 20 years ago, and the fact I've no recollection of the technique suggests it is reasonably easy. Easter's suggestion would seem likely to be what I did though.
