Hi
The ISO does have a fair bit of power, but it is controllable.
Although the boat does not reef, you can de-power it quite a bit, this is easier with new sails as it is easier to get them flat, but the same techniques will work with old sails to.
Finding a local sailor to help is a good idea, Restonguet sailing club has a few ISO sailors and some good ones at that, so maybe try them for a chat, Chris Webber is a good place to start.
Just a few pointers on how to de-power in case you want to sail before you can get any help.
Rake the mast back a bit, Rake the spreaders back, get the barber and Cunningham on hard, let the swatcher (mast gate) off, loosen the Barbers, lots of kicker.
One of the best ways to learn about your ISO is to come to an event, The Pro / Am system means that the back markers of the fleet get help rigging and tuning their boats from the better sailors, so come along. We are a friendly bunch.
Rob