Tartare, personally I would try to learn on a piston-engined helo as a starter at the bottom of the helo `ladder` ,to later turbine powered ones.Whilst you have FW experience,I would `suggest`that if you start a helo course,then minimise your FW stuff during the course,as you are/will be in a whole new ballgame.Your basic airmanship should be fine as regards R/T circuits,nav,but it will improve immeasurably flying a helo; your lookout will be sharper,you will see trees,fields,power-lines,assessment of wind ,drift,balance,learn smoothness of handling; your ears have to become attuned to the Rotor RPM above all else,for RRPM now becomes your #1 priority; too much and the blades may fly off,too little and they will `clap hands` before you can utter `fookinell`. You may well come back from a training sortie and sit in the corner of the coffee bar and slurp it out of the cup,as your hands are shaking so much; you may also be found wandering around ,talking to yourself about innane things,and people may give you a wide berth,because they don`t understand RRPM,inflow roll,translational lift,vortex-ring,pitch-lag instability, ground-resonance,etc,etc. And then the darkness will be cast from your eyes,one day,when you can hover over one spot on the airfield,do spot turns around the rotor,tail-rotor and the nose,translate sideways,backwards,and anywhere between,pull off an EOL.......
You`ll find it frustrating,maybe tiring,but truly enjoyable and almost the best fun with your trousers on....and you`ll be hooked for life..!! Go for it......