What appear as threads on the guides, are not. They aren't threaded spirals, just uniform rings to help with seal retention. Grab the old seal around the wide body area with pliers, don't get Neanderthal, wiggle and pull. You may be surprised at how easily they come off. They won't deform if you use minimal plier pressure.
Then follow Gaz64's assembly advice. I like to pre-
oil everything before pushing the new seal on.