dont bother doing it if you're sticking with the stock or hi-flow stock turbo.
if you are going to do it anyway i'd definatley get ALL of your manifold studs replaced, if they dont break now, they will later. when i took my exhaust manifold off i snapped around 6 studs and replaced all of them. nissan sell the studs pretty cheap. you'll get the full set of 12 for under $20, it'll be around the $12 mark if you're an SAU member.
anyways, dont do it if you're looking for big gains on the stock turbo. the money can be better spent elsewhere.