This will answer most questions about the swap
http://www.focusfanatics.com/forum/showthread.php?t=114486
your list looks good, just add a new power steering line as well if you dont want to bend your old one, and the oil dipstick tube needs to be replaced with an SVT the stock zetec wont work.
as for new vs used, of course new parks are great, but it really comes down to price and what you can afford and or willing to spend.