I'm sorry for your loss bud, there's no easy way in doing this.
I lost my father when I was 19, matter of fact, we were outside, playing hockey, he collapsed in my hands and I had to watch the life sucked out of him, with no power to do anything. Death is an extension of what we call life, and is a natural part, but one we ignore, fear and resent due to the pain it inflicts. It's a reminder we are simply human.
That being said, keep your head up. The pain and grief will come in waves with no time limit or warning. Your day will be coming along fine until a song or memory comes along and punches you in the gut, with the memory of your father. Look, it won't get easier, it will always hurt, but you learn how to deal with that pain and transmute it into something productive.
Right now, it's tears of pain and frowns. Soon, it will become tears of happiness, smiles and gratitude. I know you're kicking yourself for not visiting more, don't do that. Life is something else, there's no cheat code and there's no one way to live it. We can only do our best and leave the rest to "God" or the "Universe". Your father knew you loved him and that you were out there living your life.
I'm not a father myself, but I know this, for the people I love unconditionally, I want them out there, living their life, you know? Out there working, finding love, progressing to better things and so forth. To me, sometimes you have to love from afar. It's like looking at a beautiful sunrise or sunset, it's beautiful, and you have no hand in it, and you don't want to, it's doing it's thing naturally and you're appreciating it from a distance.
So, head up, cry if you need to, yell at (not people) the sky, be mad with God if you're the religious type (He can take it), hit the gym, grab a drink (not to drown sorrow but to celebrate his life) and whatever else you can.
To keep his memory alive, be the best version of ourself. In my religion, the soul is eternal, the body is simply a "cloth", that is worn for a "X" amount of time, until it is time to pass into the next life/phase/whatever you want to call it.
As long as you remember someone in your heart and mind, they'll live on forever.