hey gav, ive kitesurfed for about 3 years, ill try and answer your questions bud.
its not as hard as windsurfing to learn but there are major differences. Unfortunately mate yes you do need lessons unless you can get out with mates who will show you the ropes and stay with u. BUT i would still get lessons for the essential deep water packdowns and safety.
You can get away with one kite but most people have a 2 kite quiver. Depending on your weight a 12m and 9m cover you from 12 knots – 30 knots. Dont forgrt wetsuit, harness, board all add up as well.
Kites have evolved and some people reckon most bows from 2007 onwards are very safe and have good relaunch. BUT again thats another reason to get lessons as u will get a good idea of what is good and bad for u.
there are very good forums out there for all your questions
try http://www.kitecrowd.com – formerly flexifoil
and http://www.kiteboarder.co.uk
both very active and friendly.
hope that helps