My engine in my selespeed abarth is dead and was considering changing it, is there anything I should know about the switch over ? Is it pretty straight forward as I know there a complicated technical car?

You never updated your other thread, what was original failure or death of engine or is it still running just badly?
Is it not repairable in car like shells on big ends etc ?
Seems brave move to swap engine with another unless you know or are guaranteed the condition of the doner engine.
Have you rung likes of autolusso an alfa specialist but some engines are shared not sure if the 2.4 petrol went in any alfas, but they will.
http://www.autolusso.co.uk/workshop/engine-rebuilds-ts-and-jts.html

Was the big end , then it seazed up
I have given up on the whole repair job,
I am looking to purchase a stilo abarth selespeed asap must be low mileage with full service etc then keep mine for the spares