You can start by looking at fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfictions from various fandoms, including Robin of Sherwood. There are also some dedicated fanfiction forums where fans might share their works or recommend good ones. Another option is to check out some general fiction sharing platforms, but you may need to use the search function specifically for Robin of Sherwood fanfiction.
One interesting Robin of Sherwood fanfiction could be those that explore the backstories of the Merry Men in more detail. For example, a story might focus on how Little John joined the group and his life before that. Another could be about Friar Tuck's early days in the monastery and what led him to become part of Robin's band. There are also fanfictions that might give a different take on the relationship between Robin and Marian, perhaps showing them in more modern - day relationship dynamics while still maintaining the essence of the original story.
Sherwood is purely fictional. It takes creative liberties to weave an engaging tale, rather than being rooted in reality. So, don't expect it to be a true account of events.
There are often fanfictions that pair him with other characters from the shows or movies he has been in. Some might create a romantic storyline between his character and another, like a forbidden love story within the context of the fictional world they inhabit.
The real story of Sherwood is likely to be about the Sherwood Forest in England. It is famous for being the legendary haunt of Robin Hood and his band of Merry Men. They were said to live in the forest, robbing from the rich and giving to the poor.
I don't think it's a true story. 'A Haunting in Sherwood' is probably just a creative concoction to thrill and entertain, rather than being based on actual events.