I'm going to have to respectfully disagree with Anda here.The Fifth Concerto is not difficult compared to much of the concerto literature out there. Sonatas such as Op.53 and Op.57 are harder.
If you're wanting to play the emperor, go for it, it's not as difficult as it seems, I have performed it multiple times and it's a fun one. It was the first Beethoven I ever learned, and the second concerto I learned (Gershwin F minor was the first). Good luck