Usually, take off front wheel, unbolt brake caliper, lift off, support by a string or wire is best.to allow you to do the work, DO NOT let it just hang, unclip the old brake pads, fit new, refit unit, etc. I tend to use a metal bar, (old screwdriver)to ease the calipers apart, before removal, other wise you might not be able to get it of the disk. fitting new is not a problem. once fitted, a few pumps on the brake peddle will put the pressure back up. Job done.
If only car, get the parts before you take things apart, other wise could be long walk to spares shop.
SD
July 2011