Multi-Pure Countertop Faucet Stem Leak

Anyone had any experience getting at and replacing the stem seal on the spring loaded poppet valve in a Multi-Pure filtered drinking water dispensing faucet? If you did, was it easy to get a replacement seal?
(Multi-Pure hasn't responded to an e-mail on this...)
I installed ours through the kitchen sink's back rim about 8 years ago. Lately there's been a dribble from under the operating lever every time it's used, leaving an annoying little puddle to sponge up.
It looks like the valve stem seal is under a little threaded piece (only about 5/16" diameter) which the valve stem comes through. That piece is slotted, but it'll take some kind of spanner wrench (like a slot screwdriver with a half inch long notch up the center of the blade to clear the valve stem) to unscrew it.
Thanks guys,
Happy Holidays,
Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can smile when things are going wrong, you've thought of someone
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