The latches arent very hard to fix. Usually just gummed up from rust, sometimes a spring is broken. Try cleaning and lubing it first.
From the factory the orginal lube was white lubriplate. Over time it has gotten hard and collected dirt. If the door doesn't open get a can of brake cleaner. Put the attached spray nozzle on it. Aim it down threw the window opening and spray the lock down good. When you get the door open. Pull the door panel and finish cleaning. Then relube the lock assy.