to "appear" good you need to "sound" good. Whichever way you get there is entirely up to you. I can't understand how you can go from knowing all that stuff, then missing only 1 year and then suddenly not knowing any of that stuff. But if that's the way it is, then that's the way it is..

In any case.. yes.. re-learn your major/minor scales (and modes).. find songs with non-standard chords to practise the other 27 billion chords etc etc.. I don't know how fast you want to get up to speed again.. but really there's no "easy" way to do it.. it's just about practising..