Looking for the Name of an Old Movie

I am looking for a rather older movie, probably a 80s one. The movie opens up with this scientist driving his VW in Mexico and some Mexicans try to car-nap his VW. He has some kind of terminal illness and gets this call that the Aliens have landed in a monolith. The story develops from there, but I never finished watching the movie and I do not know its name.

I would like to know the name of the movie, so I can finish watching it - help.