I hope you enjoy your coursework and learn alot from it.
No one can really answer the question you've asked...except you. Some folks are quick to learn and intuitive about sailing and can do amazing things in very little time. Others can spend 30 years tootling around the local waters participating in beer can races, dreaming of voyaging, etc, but still not be "ready" for offshore work. Some folks will never be "ready." Most people are NOT intuitive nor savvy about the art and science of sailing. Thus, most folks rely upon years and years of experience to build a database of knowledge which allows them to safely undertake voyages.
That experience starts as soon as you can get it. So....
Getting "out there" even if "out there" is just sailing coastal in your area will really help you. Trade in the surfboarding, paddleboard, and fishing time on some quality time on a sailboat. Crew for someone locally if you can. If you cannot, then buy a small sailboat. You can pick up a used, seaworthy boat 20' to 30' from $2K-$10K and can sell it again w/o losing money. As an aside, realistically, if you don't have $2K-$10K now to buy your "practice" boat, unless you're planning on selling real estate you may own or have a big paying job, you probably won't have the cash you need in two years to buy and use the boat you plan to purchase and live aboard.
If you are planning on ocean crossing "solo" there's alot to be said for owning a small boat (30-37 ft max) rather than a larger boat like you've mentioned. It is much easier to "manage" a smaller boat alone and there are numerous older, bluewater boats available in these smaller sizes. You can "man-handle" a lot of things on a smaller boat. The sheer size of things on a larger boat often requires more knowledge and finesse in handling when things go awry and more savvy experience in properly maintainance. Not to mention money.
Taking a small boat in and out of your harbor, maintaining it in the water, anchoring, sail handling, getting used to what can go wrong on board a boat--this is good experience. You will not only gain sailing experience but also sailboat ownership/maintenance experience. With a couple years of sailboat ownership under your belt, you should be much more able to assess your own strengths and weaknesses as a sailor and sailboat owner. Then, you will readily be able to answer your own question about being "ready" for ocean crossing.
Best of luck to you.