Without knowing sail dimensions I think twice the length from the tack to the stern should be a safe guess for each sheet length.

As for instructions -- get a sock for your newbie crew, IMHO you're likely to have problems if you try to handle it without one.... especially in a building wind scenario: Typical, you start flying it in the morning in 2-5 knots of true wind, and around 12 or 1PM the afternoon sea breeze picks up gradually. By the time you realize it's time to strike it you're over-sailed, and it's a flapping handful difficult to take down without a sock to keep it under control. Whatever you do, don't fly it without the mainsail up if you don't have a sock -- the main can help blanket the spin in a take-down.