There's a video that I wish was on Youtube before I did mine. The rear was a pain for me since I wasn't sure if the tensioner assembly had to come off or not. It did though. - Which means coolant elbows should be on the parts list too if they're old. I didn't know at the time and had a coolant leak for a few days. Had to change them in freezing weather.
Impala - Valve Cover Gasket Replacement (Front) 3800 Series II - YouTube
Impala - Rear Valve Cover Gasket replacement (3800 Series II) - YouTube