GMC ENGINE OIL LEAK

I Have The Vehicle Listed Above And It Needed An Oil Change, So I Got The Stuff And Changed It. About Two Days Later My Dashboard Says...

Put My Car On And Oil Started To Leak. I Found The Leak, Just Not Sure What It Is. I’m Looking At And If It’s Something I Can Replace....

Removed Whole Top End As Well As The Valley Cover For Dod Put Back Together Had Massive Oil Leak Seams To Be Top Rear Of Engine