Tom, another good site is Tolkien Gateway...about read Quenta Silmarillion, it can be hard to read the first time, but the most important parts that you must know to play the mod are :
-The Fall of Gondolin
-The Ruin of Doriath
-Beleriand and its Realms
-Lay of Leithian
-The book of Lost Tales
-The Sons of Hurin
-The Darkening of Valinor
and many more...of course!!!
Regards and thanks for your support.