since you've got it apart I'd upgrade the manifold. but up to you. I hope you got OE Ford gaskets? For some reason thats one of the few things on our cars made right.
i have coated BBK LT.
love it. I would recommend coated for 2 reason. Anti-rust-stays good looking for looong time, and with caoted LT, it'll retain heat inside of tube, minimizing the possibility of tuning on CEL(youknow one comes on because exhaust gas cool down too much befor it picked up by O2 senser?)
After having installed my headers myself, i have to say: I can't believe your friend is only charging you $150 for that job LOL. Before i did it myself i think the lowest price i found was $300 from a Ford Tech friend and hell i think that was a good price LOL i think i'd charge more like $500 that job is a PITA.
But its completely do-able if you want to do it yourself. 2 weeks time is MORE than enough time to do it. I did mine in two 12 hour days of work on the car. And thats with reading directions step by step. (I wasn't a mechanic at the time)