To answer more precisely, you can't do such a big project aside of other tisks in your life, only a big company with very experienced designers and programmers and producers is able to finish such a project.
You can do very much with GameStudio and programm and design things that gives you an idea how to do a lot of things which are required for such a game, as there are player movement, NPC AI, path finding, etc.
To finish a game project at all, you have to aim for a very small game - but this is the case when you are working with other engines, as well.