Yes
rear main seal
Yeah, sure.
yes
It can leak oil out from the rear of the intake manifold gasket. The oil sending unit is right behind the distributor and it can leak oil too. There is also a gasket that fits on the bottom of the distributor where it goes into the intake that can leak. And the worse thing it could be is the rear main gasket leaking oil and you would have to remove the transmission to repair that.
Yes it should have front struts and rear shocks.
How do you replace rear shocks on a 2003 altima?
Rear main seal.
The rear shocks on a Pontiac G6 are replaced by supporting the rear axle on jack stands, removing the wheels, and unbolting the shocks. New shocks can then be put in place and bolted on.
Sure could. Also the valve covers.
struts in front, shocks in rear.
An oil leak can be from many different places. They include the valve cover, oil pan, front and rear main seals, and oil pressure sending unit.