Ask yourself this: If not now, when? I'm 70 now, but I bought a used long arm set up when I was 60. Like you, self taught. I have a lifelong inherited medical condition that is basically slowly killing my peripheral nerves. So what? It has never stopped me from doing what I want to do, although it has influenced how I do what I want to do - and, looking back, probably my choices of what to do. In fact, my long arm purchase was made because my arms and hands will NOT allow me to quilt on a sit down machine of any size. (I can piece, but do simpler projects and love doing it.) Replaced my now former system with a Grace Q'nique 21 with Quilters Creative Touch Beginnings. I am working hard to learn how to use the new software. My 75 year old sister has my old system.
Looking forward, I expect that in 5 or so years I will not be able to stand at the long arm anymore. But it's 5 more years of doing what I like to do. And, with luck, I will find a way to continue quilting.
Yes, you will be able to learn it. Yes, you will use it. Your friend who said her friend bought one and never used it. ...ask her if her friend will sell it to you!
Your life, your money. Do what you want!