I don't have a checklist per se, but I do have a suggestion. Pick up Nigel Calder's Cruising Handbook. Read it, of course, but also you can use his chapter headings to begin a personal checklist for yourself. Going through the chapters, start listing those things you already know/have on one side and then a second list of those skills/items, etc. that you don't know or have.
This should give you a good start. By the way, Calder's is certainly not the only book on the topic, there are many others, too -- some good, some not, but Calder's is pretty decent and has some good learning
The bottom line, though, is no matter how much you do, in the first six months you will have a number of those, "I should have ...." thoughts! But, that's part of the fun.