What Todd said, with a few more details.

Getting your high end Goretex shell back into primo shape is a multi-step process starting with the cleaning, then the re-upping of the DWR (durable water repellant) finish on your garments exterior.

For the cleaning Nikwax makes a product called "Tech Wash" which is basically a Goretex friendly soap. You can get by with a mild commercial detergent but the problem with most of these is that they leave a residue on the fabric which can clog the porous Goretex material messing up the functionality of the waterproof-breathable membrane.

Once you have run your coat through the wash using the "Tech Wash" to clean it, use a product such as Nikwax's TX Direct (wash in or spray on) which restores the water repellant finish to your garments outermost layer.

Although there is really no harm in having the shell material on your coat "wet out" as long as your membrane is functioning, most of us get a warm fuzzy from seeing water bead up and run off as opposed to soak into the outside of our coat.

Gore's Revivex product is another option for the DWR coating. In each case, follow the directions on the label. All products should be available at your local outdoor store such as REI.