DO you sing in private?...where no one can hear? Can you hear your own voice and tell whether you are 'on key'? Can you tell when OTHERS are on or off key? I can hear when anyone, including myself, is 'right', but it often takes some work...and just getting my vocal cords used to making the shapes... to hit it right.

If you can tell the difference, you can probably learn. You can't just go in and start in the middle.

Another question is, do you know some songs? After 20+ years, you ought to know WHAT you want to sing. Can you sing those songs along with others?
   I know one guy here whose singing was almost painful years ago, but he has worked on it, and does quite passably now.

Who do you know that CAN sing and can be trusted to listen and make suggestions?

Gotta start somewhere...