Can You Double Head Gaskets?

it is better to use one. two won't harm anything but sometimes having two will cause one gasket to squeeze outward and create a leak. also, two will raise the head slightly causing slight compression drop.

Can you use a metal head gasket twice?

you can reuse a metal headgasket for sure! Best is spray it with coppergasket!

Should I replace both head gaskets?

DON'T: Do only one side.

If one head gasket failed though, chances are the other one will fail because it is connected to the same cooling system, same block and same engine management system.