One way would be to 'part out' the set to a wishlist, then remove from that wishlist the parts you already own. That leaves you with a list of parts you need to buy, and you can use the site's wishlist wizard to find you the store or stores you can purchase those parts from.
If you need instructions, you can either see if any are for sale here, or visit the official Lego site and see if they have them available for download.
Comments
If you need instructions, you can either see if any are for sale here, or visit the official Lego site and see if they have them available for download.
A great set, deserves to be built!