Looking to do my own maintenance on a 2002 Mitsubishi Lancer I am looking at doing my own maintenance on my 2002 Mitsubishi Lancer. It needs two new oxygen sensors (don’t know the location) and an exhaust manifold/catalytic converter. 

Removal should be easy for the manifold itself but installation is where I feel it gets tricky. The manifold has a gasket. Would this gasket need some sort of sealant or is it kinda just placed and held together by the bolts? Is there any additional information I might need, special tools, sealants etc? 