Also i have large hands
What you do with them is what counts.
If your octaves aren't already awesome this will be a very big push.
The heroic is not around grade 8, it is significantly above that, more likely to be listed under licentiate than associate even. Not saying you can't play it, just that you're not going to do it justice within that time frame.
..Speaking as someone who did attempt to learn this work at around your age, and with around 8 years of lessons behind me at the time, having recently completed a bunch of grade 8 works.
....
I rather think the raindrop prelude, op 28 no 15 would be far more approachable in the time frame and just as well known. Perhaps not as flashy as you are looking for though?
Grieg, Op 46 No 4 - In the hall of the mountain king.
^sets a cool mood, gets pretty exciting/dramatic.. not nearly as hard as the polonaise, but 98% of your peers won't have a clue anyway.