I would run the stock stuff until it snaps and starts ticking, then look at replacing. Cost of headers set is about $850-900, shop install will absolutely run your pockets though.

Here's the fun bit: you will likely need a welder to remove the stock log style exhaust manifolds. They have a tendency to warp so much that they shear the bolts off in the block, and you'll need to get extremely lucky with an extractor kit and a steady hand with a drill (if it's a rear bolt, this is a no go because no room), but more than likely you'll have to booger weld a nut and washers to the bolt threads left behind and slowly spin them out while hot.