If your looking to make it a learning experience then be prepared to do a lot research, reading, question asking, etc to build your own kit.
You NEED quality parts; no eBay junk. This forum is peppered with people selling manifolds, turbos, piping, etc, etc. Take your time, get the best parts for the best price. Nothing wrong with used parts as long as they are not beat to hell. If the deal on parts seems to good to be true, it probably is. Take a few months coming up to speed on turbo systems in general and all the pieces that make them functional.
For the Duratec, get a quality manifold or make your own (sporadic did this). Get the appropriate size turbo for your goals (talk with your tuner about this). The piping can be made custom (just make sure it can hold the pressure, blown couplers are no fun), any intercooler as long as it fits to your liking, stock MAF will work on most mild boost pressures (add a MAFia for more). You cannot skimp on injectors (minimum Ford 42lb); they can be found used on here. You cannot skimp on tuning. You will be purchasing a XCAL device; and for god's sake find a reputable FOCUS tuner. Many people have found out that just because a tuner uses SCT for Mustangs, GM cars, etc they cannot tune the Focus. Even the best Focus tuners say tuning the Focus is different from other cars. Don't forget the proper gauges (Boost, oil pressure and WIDEBAND Air/Fuel). Things add up FAST.
If your looking to buy a complete kit, including tuning, support, etc....go with the FSwerks kit. You can have it bolted on in one weekend. You must be able to datalog properly so that Randy can dial in your tune. Once the tune is dialed in, your done. You will get 10's of thousands of miles out of their kit.
The choice is yours. If your looking for cheap boost, forget about it. Be prepared to spend a few thousand if you want a kit that can be driven everyday with no worries or issues.
P.S. - I built my own custom kit for my car. Started with the F2 manifold and downpipe and went from there. I have worked on Foci with the FSwerks kit; the quality and fitment are spot on. Just do it right the first time; you'll be much happier in the end.
2010 Ford Escape 3.0 V6
2004 F350 6.8L V10
1986 XR4Ti 2.3L Turbo
2007 ST ; formally bewst'd - R.I.P