all knowing soul rebel has spoken, everyone quickly agree with him for his opinion is correct not yours. sites and books will help you start out right, or you can get really baked and sit around and see what you can do. id say avoid getting lessons because like the guitar, most guitar teachers go 'oh i can play smells like teen spirit, i should start giving lessons'
i would think that if you have enough knowledge about playing other instruments and theory, such as notes, scales, chords, intervals, and what not, just by fooling around for a little while you should be able to get the hang of it. I have never played a sitar, so i have a whole lot of knowledge about it. maybe if you were to search something like "how to play sitar" or "sitar tips" on google, you can find some nice information.
Having played the sitar for over twelve years now, I can say it is waaaaay harder than anyone would think, perhaps THE most challenging instrument one can encounter. Since the eastern scales include notes that just arent in western music, even tuning that bad boy can be a beast. I cannot suggest finding a teacher enough, even one or two lessons are most important for the basics. I personally use a few books imported by my teacher, although they are very old and some handwritten. After a long hunt I found some tabla tapes to use for a backing rhythm, since most drummers only know how to count in fours. Telling them to do a seven or 13 beat cycle only brings quizzical looks! Unless you know a tabla player that is.... The frets are moveable, but untill you can grasp the uses of different scales, I suggest you keep em where they are. Even when changing scales there are only two that move for the most part. I suggest you try some world music dealers for books, its not the kind of thing that flys off store shelves, but they may be able to order for you. I have not looked for sitar music online, but it has to be there. However, I warn you, their tablature wont read like what one sees in music class!