Nope. King Gareth himself does appear in the second book of the Year of Rogue Dragons trilogy, but the actual events referenced in Promise of the Witch King would only have been detailed in the Bloodstone Series of 1st edition modules, and summarized in the 2nd edition sourcebook called the Bloodstone Lands, written by some guy named R A Salvatore. Dispite the fact that he wrote the sourcebook, the original modules were not his baby, nor were the early one actually set specifically in the Realms. They were tied to the Realms later, after the setting launched, and only the last ones specifically reference the Forgotten Realms and the regions around Vaasa and Damara.