I'll be doing spesh over DECV next year (only one that wants to do spesh LOL). Quite a few others (previous students at my school and a few people on here) have done it, and also done well in it. So yeah, it looks like it can be done. It does seem you would need an incredible amount of motivation though, have heard of a few people who haven't done that well since they slacked off.
There seems to be more than enough resources available. The teachers at school are willing to answer questions, also the DECV teacher and of course AN. I was questioning how helpful a DECV teacher might be, but after being on AN and being able to understand stuff being explained over text after awhile, I'd assume they would be just as useful. Of course there's Khan Academy and all the other maths resources on the internet.
So yeah, I'm pretty excited for it next year, should be pretty good. I'm not too worried that I'd struggle with understanding content, there's more than enough resources available to help with that.