Take the 2 bolts out of the bottom and the whole baffle will slide out.

To fix the threads you'll need to put in a new insert.

Harbour fright sells a pop rivet like tool that you can put a new insert in with.  But these are aluminum and won't last long.  You'll need to buy some steel ones.  The ones that are in there are pem-serts.  Don't worry about brand just get one, knock out the insert if it's still there, drill out the hole to fit the new insert.  and pop it in there.

Alternate, with baffle in hand insert screw and put a washer and nut on the inside.  

Also, USE ANTI SIEZE every time.  Especially if you're running the screws in with a drill motor which they say not to do.