Don't know the ins and outs but know it is far from a straight forward plug and play operation. Thinking mounts, drive shafts, wiring looms etc. It is pretty involved. With the mk5 Fiesta best bet would be sell your mondeo and get hold of a MOT failure Puma for £200 and drop the 1.7 out of that in as the Puma and MK5 Fiesta share the same chassis. Add a few FRP upgrades and you'll have a rapid fez!

Not discouraging the Mondeo swap, and if you have space and time to have the cars next to each other and off the road for a while then go for it. The Puma conversion really is a weekend job and has been documented very well on the forums