Check out this collection of articles: http://www.anapsid.org/pdf/icfs.pdf
Look up how to trim your ig's nails. It's the 'very' tiny tip of the claw that has the nail that's so sharp. Don't lop off any part of the claws, just the tiny needles on the ends.
It's natural and sign of good health for new captive iguanas to be afraid and resist being held. The more you handle him, the more calm he will get, but it can take months of practice. You have to get good at quickly grabbing him up, pressing him into your waist until he stops struggling (30 sec.). Carry him to a chair or sofa, sit down and wait while you hold him. He will sporadically try to escape but don't let him get away.
After a dozen or two repetitions of this he will start to sit still a few seconds while you slowly loosen your grip. Clamp down when he lunges. Eventually he will stay still for longer. When he does that, you can let him walk off of you to explore.