TRANSPLANT? 316 COMPACT -2.5?

[BabyCompact316i]

Hi boughty the baby compact for a run around back and forth to work and it has no power anyway last night on the way home temp gauge went stragth to red and checked this morning and water in the oil and radetor water is brown like rust so the head gaskets is gone so i hav a excuse to get rid or transplant a 2.5 or 2.8 in to her !

so i what i would like to know is 1, can it be done ,2 , how easy ,3 what do i need i.e wireing loom ? gearbox? diff? prop shaft , Brakes upgraded or is simple change over ?

please guys need help and fast. what will cost do you think.