Bad rod bearing
 

My aunt has a 06 mazda 6i and has the 2.3 and a rod bearing went bad in it. So i am going to be replacing them for her, but their is this big block attached to the main caps i have never worked on one of these cars so i have no idea what it is and want to make sure i don't break any thing. Does any one know what it is? I have to remove it to get to the rest of the rods. Any help is greatly appreciated.
Thank you
Tony