Welcome aboard and 'Welcome home' from a brother in arms(Vietnam '70-'71)
I know exactly what you mean by being back in the World and bored outa your mind. Circle track will feed your need for that 'combat adrenaline' fix, guaranteed ! As you are used to, "Prepare-Practice- Prepare- Practice- Prepare" and you will do good and have a blast!
Legends would be an excellent choice as they are super cheap to run after the initial purchase price. Get a turn key car instead of a bunch of parts'n'pieces. That way you can focus on learning how to drive. Ask LOTS of questions ! Hook up with Legends racers at the track and you should be able to locate a running race ready hot rod. Don't take the racing tooo seriously tho ! HAVE FUN !!