maybe im just arrogant but I think thats totally possible in 10 months. Once you get the basics down for things such as proper fingerings moving up and down every mode/scale, and basic chord shapes (drop2/4 and 1735 voicings and all that crap), its not that bad. Also, I feel that doing covers of songs, its easy to learn covers in short periods of time, what takes years to do is your own songwriting/really good improvising IMO.
Of course he probably had some knowledge of music theory before hand, probably played another instrument..
plus that keyboard is so ....in awesome sounding/looking, i would probably even learn all the DT solos on it o-O