Hey guys first let me say thanks for any and all responses. I just bought this 01 2.9 n/a s80 great car just needs a head gasket. So i have it all torn down and ready to take the valve cover off. I just have a few questions before i do so.

1. Why do these cars need a rear cam lock tool? And what does this tool do exactly.

2. Do i 100% need to remove the cam sprocket to do the headgasket to do the headgasket ? Or is this only necessary if i want to replace the cam seal.?
Thanks again guys for your help
P.s i live in colorado so if anyone has the rear cam lock tool and would rent it to me just message me .