You should at least get the PE railings to add to the ship. I would get the gun barrels because they are far superior then the kit ones.
As for rigging I used EZline fine, both black and brown. Black for the radio antennas and brown for the flag and signal lines. The main problem during rigging installation is getting the rigging taunt. EZline is flexiable so you can stretch it a little during gluing and it will stay pull back and give you that taunt look. A modeler skill with using fishing line can get the same effect, but I am not one of those so EZline makes up for it for me. Make sure your masts and yardarms can handle the tension. Some plastic masts and yardarms are so weak the slightest tension will bend them. I had to change a few masts and yardarm on ships with brass so they would not bend under the tension.
As for weathering that will depend on how you want to display the ship, just out of the shipyard or weeks or months at sea. Ship hulls and main decks gets the most weathering with less weathering as you go up the superstructure. I suggest you look at photos of ships and how the weather has effected their paint work.
I mix my paints at a ratio of 81% base color with 19% white. This will give the paint a faded color that weathered paint take on after being at sea for a while.
Oh, and one other thing, build up and then out when doing the assembly. Nothing worst then knocking stuff off or breaking things off while working on the upper decks and superstructures.
Good luck, and don't forget to post pictures.