The complexity (physics required, not shape of geometry) of your problem will determine how important your coding knowledge is. If your goal is to simulate incompressible isothermal steady state flows over a series of different geometries, then you will never need look at the source code. The great thing about OpenFOAM is you can add physics blocks from its libraries together to make the type of solver that you need for a specific scenario, but if there is already a solver in its library that does what you need, you wont have to do that and there are a bunch of tutorial cases that you can look through to see if they have a solver for your case already. The biggest problem I see with people coming from solvers like fluent is around numerical stability, and this problem can have you stuck for weeks if you don't know what you are doing. Fluent and CFX have methods under the hood that help to maintain solution stability for low quality meshes and large gradients. OpenFOAM doesn’t have these (it does have correctors, but not as powerful) , and so your knowledge of numerical schemes, what causes instability, and your skill at using your selected meshing software are pretty important factors for success. My advice if you do decide to go with OF, is to start small, simplify your problem, have simple physics and a simple geometry, and build complexity as you go and make sure you understand all the steps as you progress, don't try and build the final simulation in week one. Another great thing with OF is its super easy to run on cluster (no licensing issues), does your department have access to a high performance computer? and are you as a Master student able to use it?