having been done 例句的疑问.

the应当是they吧?
被告知前面（指后面几天）天气不好后,他们改变了路线.
这是一个简单句.前面是现在分词短语作时间状语,修饰changed.逗号后面是句子的主要部分.
前面不是从句,因为从句也要有完整的主语和谓语.而这里没有主语.
having been told 是先于changed发生的,所以用了完成时的形式.否则应该用being told .
having been told 不能说成had been done.因为had been done不是分词短语,而是动词的过去完成时的完整结构,这种结构只能做谓语.
如果硬要用 had been done,那只能将这个分词短语改成一个从句.即：
After they had been told that bad weather lay ahead,they changed their course.