How do i fix my peugeot speedfight exhaust problem?

Hi, I'm not very good with anything engine related so bare with my 'lingo'.
The part that is linked to my exhaust (the bit that the gasget is joined with the exhaust to) has a larger crack along the bottom half of it.
It looks like the bracket that was supporting my 100cc (x-speed 03 model) speedfight has broken so I'm thinking that the exhaust was only being held on by the 2 bolts in this area and now its VERY loud and as a result it won't go very fast. I've stopped using it, as I'm sure it won't do it no good.
What I'd like to know is that part i don't know the name off (is it the mainfold or am I way off?). Would an engine n00b like myself be able to change the part?
And if so, HOW?
This is how I must have brought the bike as I haven't dropped it on either side.

I hope this makes some sort of sense.
Thanks