There is actually a web site to rate the difficulty of learning different languages for "English Speakers". I am not sure how this changes for those who were raised on Valleyspeak rather than English.
My recent hobby is Hebrew which supposedly requires 1,100 hours of formal study to achieve "general proficiency", whatever that means. My two semesters of Hebrew provided about 160 hours each of study, which is less than 1/3 of the goal, although I doubt that the US State Department is measuring their training hours with respect to Biblical Hebrew. Theoretically the 1,100 hours could be achieved by averaging 3 hours a day for a year. There is a third semester of Hebrew at my seminary that I hope to take in the summer, but this would still leave me less than half way to proficiency, especially given that learning languages is less efficient per hour when it isn't full time.
So where to go next? I can't take off from work for a full time program, nor can I find a local tutor. The Pimsleur recordings have been helpful, but 90 30-minute lessons works out to 45 hours of listening that expands to about 150 or so with review, but still leaves me far short of the goal. A web site I just stumbled across is from the University of Texas which has a variety of additional learning materials for modern Hebrew.
There is the question of why bother doing this. The little I know has been quite helpful on understanding why there are different English readings of the old testament. Still, what I know isn't nearly enough, yet I did well in my classes. Most pastors don't bother to study Hebrew. Then there is a note in my Hebrew Bible's preface which gives a statistic that only 20% of pastors who studied Hebrew retained it. The end result is that pastors who can really dig through the old testament in the original language are quite rare. So the overall goal is to achieve a level of proficiency that will permit me to engage regularly with Hebrew, whether on the web or reading my Hebrew Bible.