Replacing the pads is easy...
you need the pads, winding tool, or large G clamp, jack, wire coathanger, copper grease and a hex key set (10mm?)
1) Pop the bonnet and take off the brake fluid reservoir cap
2) loosen the wheel on the ground
3) Jack the car up
4) remove the wheel
5) find the 2 hex bolts at the rear of the caliper and loosen them off
6) wind back the piston
7) remove the spring clip
8) Bend the wire coat hanger into an S shape, and secure the top of the hanger to the suspension spring
9) lift out the caliper and secure the caliper itself to the bottom of the wire coathanger...
remove the old pad, and apply copper grease to the new break pad at its contact points with the piston and the caliper
10) re apply the brake pad to the caliper, and repeat on the opposite side of the caliper.
Re-attach the caliper in the reverse of the above. and then move onto the next wheel.
I did this on my first go on my last focus in about 30 minutes on the two front wheels. It really isnt a difficult job. just do a quick google search on "changing brake pads on Focus" and you will find a few videos that also can be very helpful.
just remember the golden rule - NEVER DANGLE THE CALIPER BY THE BRAKE HOSE!!! always ensure that the brake hose has slack at ALL TIMES!!! remember this and you wont have any real trouble