Kevin -
I beleive the lines are 1/8". Just cut a short piece off and bring to your boat shop. As to the length get a total of 4 pieces 6' long and cut to fit. I use two different colors to tell the crew which line to pull (teal to pull up & purple to lower). As to the weaving just untie the stopper knot in the rudder blade and sew the new line on and just pull the other end of the rudder line (which has the ball or T-handle on it and it will thread through.

Paul