Most people will tell you it is a rule of the thumb to never reuse a gasket. If it was me I would most likely replace it just as a fail safe. Cheaper buying a head gasket then a whole new topend.
EDIT: Also, as for a torque wrench the only time you really need to use one is when assembling the motor such as your head nuts. It is very crucial or you can run inot like in your shoes, a leaky head gasket.
Also after "breaking in" a new motor make sure to RETORQUE the head nuts after a couple of hours.