any lithium grease will work fine, you can even get it from
Moyer Marine Atomic 4 Engine Rebuilding and Parts (the atomic-4 God)
You should be able to remove it by grabbing it with a small pipe wrench and turning it counter-clockwise (righty-tighty-lefty-loosey) be careful you don't crush it.
If you do, you can get a new one here...
Grease Cups
I think its 1/4 in pipe thread.
yea, 1/2 a turn sounds about right.
Moyer says one turn every 8-10 hours...