If going anymore than stage 1 unless you uprate the turbo and have group A head gaskets, it's not going to last long. You'll also need a bigger intercooler ideally (or a charge cooler). PJ motorsport has a good bit on it's website about the basics.
http://www.pjmotorsport.com/stage2.asp

Personally, with a 2wd, I'd go for a stage 1 and wait for the engine to go wrong or you get bored before going stage 2 or 3. You don't waste any money this route, other than having to buy another chip - otherwise all stage 1 parts are used in stage 2+. Read up in Fast Ford or Performance Ford for a few months before you decide the best route, as if you do it wrong and overtune an engine not up to it, you'll end up with a £4K plus rebuild bill.....

A 2wd Cossie will last really well on a Stage 1, but if you like to give it some and go for a better tune, they can spit gearboxes and diffs if they are original items with 60K+ miles.

Have fun and hope this helps