I am not a computer engineer, I don't have any Microsoft certifications, but I do use a computer all-day every working day. I do word processing, spreadsheets, data acquisition, retrieval, and manipulation, not-much digital imaging work, and payroll and human resources for about 100 people a semester at the place where I work. We have nearly 500 students a semester whose paperwork I have to track, access, store, retrieve, and check.
I have a Mac desktop, a Mac Pro laptop, and an iPad. At home I have a Windows desktop and I actually find using a Windows computer easier for me, because I have used Windows-based products more-than I have Apple.
Your local adult-education classes for your school district will probably have classes at minimal cost you can take, and there are no grades, it's just about helping you to learn how to use your system better.
I agree about modern computers, a few hundred dollars gets you a great desktop, but generally the laptops cost much-more $ esp. for Apple, as-noted. I would advise getting a new Windows and take that adult-ed class, they probably have a number of different classes you can take based on what you want to do w/your computer.
When I have problems w/my computer, I ask my son, who has a B.S. in computer science, or my wife or daughter both of whom are EE's (electrical engineers, my wife deals w/transmission for utilities, and my daughter's majors were computer engineering & EE) or, I take it to a local shop where I get things fixed w/o having to ask a family member, and the repair is usually faster because I don't need to deal w/the family obligations interfering w/the needed consult.
Get something new and affordable, and take those classes, and then just use it.