Most shearers will cut the sheep, its how it is unfortunately. Some places, such as the ears, bleed buckets from tiny cuts, making it look much worse than it is! It depends on how dirty/sticky the wool is and how sharp the handpiece is on how much the sheep gets cut up. If you take is reallly slowly on a clean sheep it isn't too bad, but if they haven't been shorn for two years they will have a lot fo wool on them, which may make it harder to get a clean clip. My dad used to shear and woolclass, nowadays he only shears the three sheep that live at our PC, and will lend a hand at crutching time. For general shearing an electric handpiece is used. Do you have a shed or somewhere set up for shearing? If not you might need a generator.
Have they been crutched or wigged in the time since they were last shorn? If not, you should look into it for the future... if they aren't shorn and crutched regularly they can go wool blind, get floyblown, get dags... Mostly its not nice! :] Crutching is a quick job, just taking the wool off around their bum, pizzle for the guys, and around their head so they can see. What breed of sheep are they? Sheep such as Suffolk, Dorset etc won't need to be wigged but Merino's will.