1995 GMC K1500 4x4 P/U - Starter

I just went to change my starter and was hoping that someone can take a look at my picture and tell me how to proceed. The starter is held in place by two bolts ("Red") but I need to remove the black part underneath (marked in "Blue") before I can do that. I started loosening the two nuts ("Green") that hold this part in place, but before proceeding any further I need to make sure I am going about this the right way. Any help would be appreciated. Thank you in advance!