Have you decompressed the brake piston? I've got a large 6" C-clamp and short 2x4 that I've used to push the piston and let off the pressure. Be careful since decompressing too much can overflow your brake fluid reservoir. You might have to drain off some fluid.
I don't know about the Focus but on most vehicles, your caliper will be hanging by the brake line afterwards. A good reason to have a few feet of baling wire close at hand to hang the caliper once it's removed so you don't have all that weight on the brake line.
In the driveway...11 M2 (mine), 09 Focus (daughter), 02 Miata (my toy), 10 GMC SUV (spouse), 00 Focus (son)