Aerospace engineering is pretty hard but not the hardest field. 

Most of the subjects are based on physics and maths. If you have good knowledge of the same, you won't find it much hard. Electronic and electrical theory are something that some people find hard. It won't be that hard as it will be if you choose to specialise in avionics.   If you're passionate enough to take up this course, you'll most probably be successful and pay is also pretty good, it was estimated to be around $105k worldwide average as the market is in demand of aeronautical engineers.

Hope this helps, all the best for the future.