Do I need to torque the screws on the headers or just make sure they are tight also anything else i need to know when reistalling?

I would think there would be a torque setting for them, maybe even some anti-sieze. 525 heads are aluminum and the headder bolts I think would be stainless. I'd check with a Merc manual or tech on both for sure.

Definetly torque them and use loc-tite. Mine all came out after my engine rebuild. My mechanic reinstalled them with loc-tite and lock washers, if the bolts don't already have them. No problems since.