Issue in your introduction
I thought that massive changes among organisms are over long periods of time.
Actually, some evolutionary events can happen on a very short time scale. A single mutation can have a massive impact on the phenotype of an individual (see for example Doebley 2004). If this new phenotype has much higher fitness, then the mutation might spread over the whole population in a matter of weeks (typically if the population is not too large, without barriers to gene flow and more importantly if the generation time is short).
This is caused by, to my knowledge:
evolutionary pressure typically encompass natural and artificial selection, mutations (regardless of their mutational effect, that is regardless of whether they are beneficial or detrimental) and other processes that you don't mention (such as genetic drift for example; you have now edited your post to include drift).
Answer to your questions
Will mutations be the only factor in human change?
By "human change", I will assume you mean "human evolution". The answer is: no, mutations are not the only process that leads to human evolution. All standard evolutionary processes are at play in humans as they are in other species. You might want to have a look at the posts Human Evolution in Modern Times and How is evolution possible in contemporary humans?.
Will humans change at all over a long time?
Yes, humans are currently (and will continue to do so in the future) evolving. Again, you might want to have a look at the linked posts.
Want to know more?
Your questions are quite introductory and show a number of misunderstanding you have about evolution. I would recommend having a quick look at Understanding Evolution by UC Berkeley which is a very introductory course to evolutionary biology that is fast and easy to follow.