Even if you only want to make small modifications to an existing application, you will still have to have some grasp of a programming language so you have a basic understanding of what is happening in the code. The core concepts of many programming language overlap so once you've learned to use one language, learning to understand and modify another is not actually that hard.

If you are going to start on a computing project you definitely need to learn a programming language. For supercomputing environments, common languages have been C and Fortran because they usually give the best performance. However, the concepts and increased flexibility of modern computer languages mean they are becoming more and more common...so if you are really starting from scratch I'd suggest you use C++!