Engine swap, should or shouldn't?

Today I took the car with the mechanic in order to clean the injectors and see an oil leak the car has. I gave him a call and told me that it has to check the engine to see if only the piston rings are the problem or needs something else too(The car sometimes emits white smoke when revving up and the oil dirp comes from the manifold, probably from the 6th cylinder since it was the one with oil when I changed spark plugs).

The engine in question is an old VG30 with at least 188K miles and 33 years+ of service. The mechanic said that it would be less expensive to find a different engine that repairing this one since it's old and it won't be too hard to find a Nissan engine.

My questions are two, Should I try to find another engine for the car or repair the current one? And, What could be the problems of having a different engine?

P.s: I can't or better said, It's not affordable for me to buy an used car here since most of the cars illegal (The cars were exported illegally since the city is close to the border of the nation and are way cheaper than one from a dealership). And the used cars from another country that are legal can only travel up to a certain distance, which is okay but there's a lot of requirements to have.