Like you, I have a background in software development, though my preferred language (by far ) is C++, and I’ve been at this for over 30 years (before C++ existed).
Unity is an excellent choice. I say that with some disagreement with C# as a language choice, but my complaint in that regard is minor considering the results.
Having a C# background is a definite plus. Student otherwise learning everything all at once tend to get the notion that scripts are a programming concept (they’re just the text files in a solution, really), so they tend to think in terms of scripts instead of classes, and so limit their thinking. You’ll have the opposite problem, which is better. You’ll think, as do I, in terms of developing an application, where C# is fully available in the context of using Unity classes.
I’d suggest you get Blender, a 3D modeling tool. If you or a family member is in high school or college, you can get a 3 year license of AutoDesk products, so 3DS Max and Maya are excellent options. They are not intended for Unity, they work to create models Unity can import. You can start without these tools, if your graphics are limited to boxes, spheres and other built in Unity shapes.
You may also want for Photoshop, but there’s a free open source tool called Gimp that might suffice. This is used to edit photos used as textures.
There are, of course, assets you can purchase in the store.
You might need a few months to learn and develop at the same time. I can’t say easily, because a lot is up to how fascination leads to diversion and expansion of your design goals.
Google, Unity forums, Unity answers combined are likely most of what you’ll need, along with the many free tutorials, some on YouTube. You may not need to purchase study materials, and I have no experience with any of them. I come from experience in a number of fields, film and television post production among them. Our mileage will vary a lot.
I can attest, though, that among the engines you might find, Unity will offer about the fastest zero to functional state of all of them. I’ll avoid specific names here, but Unity is remarkably good at that balance between ease of use, results and target hardware variety.
You didn’t mention sound. Don’t forget sound. Sound effects, maybe music, etc. Sound is an easily overlooked dimension for a student coming on board. I have a midi keyboard, music workstation, etc. That may not be necessary, but if you’re not musically trained, you might want to find a friend that plays keyboards.
As to sound effects, there’s an anecdote that’s quite informative. Use your imagination. It is a fact that the original Star Wars sound for shooting those laser weapons was created by attaching a microphone on a guide wire holding up a telephone pole and striking the pole with a metal object.
You would not believe what artists who specialize in this art do to get sound effects. You can do a lot with just simple beeps, blips and such, all created on a synth.