I've been down this road a few times. You just need to remove the manifold and replace the studs properly. I don't think the manifold-to-head bolts will give you as much trouble as you think. They are usually in fairly decent shape, not rusted and corroded like the collector studs are. Take your time and use the right tools. If they are six point bolt heads, use a six point socket or wrench, get a good clean grip on the bolt before cranking, etc.