CAA69

hello guys , my 09 plate xf , had a coolant problem ,so I changed water pump & the plastic housing that sits top /central of engine ,,just before I drove it in for repair work ,the oil pressure light came on , so I topped up the oil as it said it needed one litre on the system ,,now it doesn't say to top up oil ,but oil pressure light is still on ,even after leaving it 30mins i restarted engine & it's still on ,,help please

Hello my jag xf 09 plate , was losing coolant very quickly a mechanic at my work noticed a black plastic housing that sits central to the middle of the engine it moves easily & when u shine a torch down you can see the crack , does anybody know how easy it is to change as it appears surrounded by a lot ,,many thanks .