1. It really depends. They will both cut sheep if you are not careful. I had my ewes sheared at the fair for a sheep shearing demo, my 2006 ewe was sheared with hand shears and my 2009 ewe was sheared with electric clippers. My 2006 ewe had gotten cut and had a flap of skin just kind of hanging there. My 2009 ewe got nicked, but they were more like little scratches that bled a little. And these nicks/cuts came from a highly respected shearer who even competed in NZ for her hand shearing skills. And personally I like the look of a clipper shearing better than the hand shears. Shearing with hand shears leaves the fleece uneven and about 1/4 to 3/4 of an inch. Electric clippers tend to go right to the skin.
2. You can shear a sheep when ever it is convenient for you. My sheep will be getting sheared in April this year, because that is when she is doing her Maryland clients. I don't know when in April, though. We've had sheep shorn as early as mid March and as late as early June. I like shearing them earlier because the later you do it, the more they pant in the hot May weather. If you have adequate shelter a Feb or March shearing would be okay, too.
3.
http://www.premier1supplies.com/img/instruction/41.pdf should give you a basic idea. You can even contact your state sheep association to see if they are holding any shearing clinics. I know the DelMarVa region is holding a sheep shearing school. I may sign up for it, but I'm afraid I wouldn't have the strength to tip half the sheep there!

I can tip my lambs, who are about 80 lbs each, and I can tip sheep that are up to about 120ish, but once they hit the 150 lb mark, uhhh no way lol. They're too big and strong to manipulate onto their butts!