depressurize fuel rail first, don't just unscrew the fittings. spraying fuel has the ability to either ignite extremely easily and also i've found that it has the ability to irritate the skin and eyes quite a bit. you'll lose whatever fuel is in the lines, have something there to catch it, believe me, theres alot in those lines. doesn't matter about full or empty tank, gravity is against the fuel leaving the tank, once it stops comin out of the lines, thats it. then just put the new one in its place, noting proper flow direction, and you're done. be sure to remember, this is required maintenance every 20k.
(off topic, thanks for remindin me, my 98 could probably use a new one at 88k as well! :P )
also, as always, be sure to exercise the highest level of safety when working with gasoline. i've found that things can go wrong...real fast.