It doesn't matter how much it changes though. The concept of 3D modeling never changes. You won't ever have to re-learn anything, you'll just continually have a better program to use.
No matter what program you use, your models are basically just lists of vertices, and their associated data (bone weights, vertex colors, UVs, etc...).
OpenGL is OpenGL, and has nothing to do with Blender. Blender is for making art. OpenGL is an API for drawing graphics to the screen. You can learn them at the same time without any interference.
I tried this and failed. It is easy, as Daaark says, but in the end I just had to admit that I am not an artist. I followed any tutorial I could find, but my mind doesn't work in the manor required. I tend to focus on mechanical details and can model mechanical objects with ease, but cannot get the hang of organic modeling.The difference between a good artist and a failed one is that the good one was willing to put in the work. Watch videos of people doing organic modeling and you'll get the feel for it.
You can learn a lot just by finishing models and scenes, regardless of how bad you might think they look. The model something else, and you will get the hang of it. Use reference pictures and mood boards as much as possible.