How deep you need to dig is going to depend on how long it's been before the contaminated oil was drained... if it was sitting the whole time I'll pull the engine and inspect the rod and main bearings as they've probably been eaten. If it was promptly drained there may be pitting in the bearings but it should run well enough for a good amount of time, especially since it's N/A.
No, if you're just working on the top end you do not need to pull the pulley... only need to do that if you're doing the timing belt or pulling the crank out.
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