It doesn't really mean anything, especially if it is your first pregnancy because you usually thin faster than you dilate with first pregnancies. I was 80% effaced for 4 weeks with my first. Sweeping your membranes is when they separate the outside of the amniotic sac from the cervix, so yes you would still need it. Hope this helps!
Also it doesn't mean that you won't go into labor either. You never know!