Easy. Probably:
Remove wheel.
Remove calipers (generally 2 bolts). Don't let the caliper dangle by the brake line though tie it up.
Unclip old pads and push caliper rod back in (you can get tools to do it easily for £15 but you are bound to have something lying around the garage to do it).
Clip in new ones (Put some copper grease on the back to stop it squealing)
Remove disk retaining screw.
Pull of old disk and put on new one. Replace Screw
Bolt caliper back on
Replace wheel.
Drive gently to bed them.
Shouldn't take more than 2-3 hours taking your time (an hour second time round) and will probably save £100 or more.