Lost my rear brake

Unfortunately, I'm not mechanically inclined. I know I lost my rear brake on the drive home. Not sure of what else. Thankfully, I didn't have a 70mph stop on the highway, because I saw what happened at 45 when I finally stopped in the middle of an intersection. Can anyone point me in the right direction of how to fix this (crossing my fingers it isn't severe)? I noticed the gap in the seam in the top right.

Valve cover Gasket not installed correctly. Rear brakes not bleed correctly. Dealer special. No it is not the end of the world. Easy fix.