From what I understand It is easy to play guitar if you know how to play piano.... but not sure about the reverse... I hear piano is very difficult to learn
about 6 months with regular practicing like doing scales and and arrpeggio's(can't spell)
Well, if you can read sheet music well it will take a lot less time. If I were in your situation, I'd just memorize it over the course of a month or two. That should help out, but that is gonna be a really tough song to learn if you've never touched a piano before. After you learn the notes, it will be key for you to execute the phrasing and the dynamics well to get it to sound like it does in that video. Hope that helped
ive had to play piano, well keyboard alot since september due to doing alot of work in a recording studio at uni for music tech, And since then ive been playing like i dont know an 2 hours a week tops, and ive learnt pretty quick. and its really handy having the knowledge from playing guitar and being able to transfer it. Thats my experience anyway.

i dno how long itd take you to learn that but if you play more than i do in a week, i'd be guesing you could play it Properly in about 5 months, but only if you put your mind to it.