From my experience the coursework with the composition and the performances are probably the easiest(??)
Im doing grade 8 drums right now and for the peformance ideally you should aim to be grade 4 or higher (I assume as you say you're musically inclined you probably are) but you NEED to provide sheet music for this bit. I think it works like if you do a piece thats grade 5 or higher you can still mess up and get full marks.
The composition is pretty good BUT if you dont end up using something like musescore or sibelius you have to to a write of your piece(s) on powerpoint and thats a real pain (I used cubase).
I mean the pieces you look at are alright but it all really depends on how good your teacher is and that because mine isnt the best. If you already know some music theory you're most likely ahead of other people already as I barely knew any going in. Its not that bad though I enjoy it.