By Jason Cochran
Updated December 05, 1997 at 05:00 AM EST

1776 is the most enjoyable history lesson ever. After getting great reviews last summer at the Roundabout Theatre Company, director Scott Ellis’ revival of Peter Stone and Sherman Edwards’ surprisingly entertaining 1969 musical about (of all things) the writing of the Declaration of Independence moves to the Gershwin Theatre on Dec. 3. As John Adams, Brent Spiner (Star Trek: The Next Generation) sings as authoritatively as he debates the slavery issue with the other founding fathers. Paul Michael Valley plays Thomas Jefferson as a horny reluctant hero, and Pat Hingle makes for an amusingly wizened, seen-it-all Ben Franklin. A