I've just changed both dipped headlight bulbs on my 2002 Ford Focus. After much struggling I found that the easiest way to do this job was to remove the headlamp assembly. This sounds like a major job but it isn't. It took me around 15 mins. per headlamp.
To do this you need a 10 millimetre socket with an extension, a ratchet drive and a Torx bit and driver.
Take care not to touch the new bulb with greasy hands, use a piece of tissue to hold it.
First remove the Torx screw holding the bottom of the fibreboard inner wing to the metal part of the wing. This will allow you to pull out the fibreboard sufficiently to get your hand up the inside of the wing. Feel around until you find the head of the 10 millimetre screw which secures the bottom of the headlamp. It's not difficult to find, the head faces towards the inside of the wing. Undo and remove this screw.
Next remove the front grill (the one with the Ford badge on it). This is done by unscrewing the 10 millimetre screws, one at each end, using the socket and extension then using your fingers to release the clip at each end which holds the grill in place.
Remove the two black screws at the top of the headlamp which hold it in place and carefully ease the lamp upwards and forwards until it's clear of the bodywork. Do not pull too hard or far as the cables to it are not very long.
Now you can easily reach everything as well as see what you are doing.
At the back of the headlamp unit, push down the clip holding the plastic weathershield in place and remove the weathershield by pulling it outwards and down so that the lugs at the top come out of their holes.
Remove the electric plug from the bulb to be replaced then release the wire clip holding the bulb in place and pivot it back to allow removal of the bulb. Note which way the bulb fits into the headlamp.
Place the new bulb in the headlamp making sure that it seats properly and re-clip the spring clip to hold it in place.
Re-fit the electric plug and replace the weathershield, first making sure that the rubber gasket is in its grove properly.
Re-fitting the headlamp is a reverse of the removal procedure, once you have located the lamp back into the car body I'd fit and tighten the screw inside the wing first, before tightening the two top screws.