How to change seals in WP forks.

-Front wheel, brake caliper and fork guards off
-Loosen top triple clamp bolts and break the caps loose
-Remove forks and unscrew the caps the rest of the way
-Pull down the fork spring and insert a thin (8mm max) 22mm open end spanner on the cartridge to hold it while you break the caps loose from the cartridge.
-Pull the cap off and the long hollow aluminium rod that runs down the middle of the cartridge. Remove the spring
-Dump oil out, pump the cartridge, dump some more, repeat until empty
-Pull the dust wiper down
-Use a small bladed screwdriver to get the clip out from under the dust wiper. There's a pointed end and closed end on the clip. Work the pointed end with the screwdriver.
-Hold the fork horizontally with the lower tube in one hand, upper in the other. Push
them together a few inches and draw them sharply apart. Do this until the fork halves
separate.
-Remove bushings and spacers and keep them in the correct order. The lower 2 bushing look a lot alike but they're not the same. Also note the way the seal faces (open side up) so you don't get the new seals on upside down.
Reverse to reassemble. Make sure you wrap the top of the fork with insulating tape to protect the new seal from getting cut up when you install it on the fork. Also,
use some grease on the new seal and dust wiper. Having a seal driver is very handy for driving the bushings and seals in correctly – see below.
When you fill the forks with oil (5wt is std, 1 litre does a pair of 43s, 1.25 litres for the 48s), make sure you don't put any down the middle of the cartridge, where that hollow rod goes. The hollow rod needs to be seated correctly. Wiggle it around until it drops to almost flush with the top of the cavity.
The way I fill them is I fill the compressed fork with oil up to the top of the inner
tube. I pump the rod right away a couple of strokes and then top off the oil. Then I
continue to pump it until it's smooth all the way through it's stroke. Then I raise the
outer fork tube to dump any oil that may be between the fork tubes back into the lower tube and then set the oil height at 120-130mm. (140 to 150mm on 43mm fork) Repeat raising the tube and checking height until the level stabilizes. I use a large syringe and short length of pipe cut to the correct length to set oil height.
Make sure you work in as clean an environment as possible. Clean the springs, etc before reinstalling them. Also, use brake cleaner, etc to clean the fork clamping surfaces and inside of the triple clamps before mounting the forks. That will keep them from twisting too easily on your next big off.

Seal Driver Tool
Use plastic waste pipe from B&Q or wherever. Don’t worry if it is smaller diameter than the forks.
Cut one length 60mm long, one length 55mm long. Wrap a sheet of paper around the plastic tube to ensure a straight cut.
Slit both along their length once.
Open up the short one and pop over fork
Open up long one and pop over the other one so the end away from the seal lines up. This creates an undercut ledge so the lip of the seal is not touched.
Put a jubilee clip around the lot to hold it together real tight & clamp it to fork.
Slide fork leg into fork outer to drive seal into place.