Yes, porting and coating the stock manifold is better than going with a tubular header on the stock turbo.
The car shouldn't be down for the porting - just purchase a used manifold locally or on EvoM and have that ported/coated so that there is no downtime. It's not typical to port the intake manifold on a stock turbo'd/mildly-modded Evo, but that's up to you.
Whoa, no, don't port the head when you do cams - that's a crazy expense and mod for the stock turbo. The stock head already outflows the stock turbo by far, so porting it would make the stock turbo even more inefficient. Save that for way down the road on a big turbo, imo.
Stick with basic mods up to 400whp or whatever, then worry about the more advanced mods that typically give less hp/$$.