The reading of the will took place in the lawyer's office .这

是的.你说的也没有错.他们是一个整体,都是主语部分.
the reading of the will ...= Reading the will...
很多动词转化为动名词都是这样的结构：the -ing of sth.
e.g.the making of cars 汽车制造
the building of the school 学校建设