It's relatively easy provided you have done a brake job before as you'll need to bleed all the brakes back to each wheel cylinder - while you're at it you might as well drain the fluid completely and upgrade to a full synthetic. Once you hook everything up and tighten the fittings, check and retighten on the ABS unit as mine leaked once the unit was full of fluid. Oh and as with anything that has an electrical component, you should disconnect the battery when you swap things out.
-- John