can i conver a 1.8 petol to a td4 with just the engine and loom or is there more to it??

need some info on how to confirm head gasket on way out

my 02 1.8 petrol freelander is starting to use water and a little oil. it is still pressurizing and running fine but i think the head gasket is on its way out. how can i check if it is... and are there any better engines i can put in without changing the whole loom ?? help please.

i need some help with my 02 freelander 1.8 petrol.. yes its loosing water and a little oil but it hasnt over heated YET !!! is there an engine replacement other than the same engine i can go for.. or a procedure i can go through to resolve my problem after i chance the c/head gasket ??? HELP PLZ