I'm trying to think of the word that means "a large task, almost more than is easily handled, but not unpleasant." The sentence that I am using it in is this:
I know that the number of topics and information within each topic to be covered seems to be a/an _______________ task, we will work through them as we are able.
Arduous and Herculean don't seem quite right. It's not insurmountable.