Ravens_nest's advice was pretty sound (no pun intended). I've been a musician from a pretty early age and currently play violin and sing (though I've learnt a pretty wide array of instruments). What I'd recommend is that before jumping into lessons, establish your range and if possible your style. It is essential to make sure you can sing in tune before you go anywhere else. I wouldn't recommend singing along to songs at first as you may not be sure whether you're getting it right or whether the singer of the song is getting it right (it sounds stupid but trust me, this is why a lot of people suck at karaoke).
For a time (over about 5 years) I did have singing lessons but I didn't have them regularly. I was singing in a professional choir at the time and every few months I'd have a singing lesson just so I could be told if I was doing something wrong and how to not do it and also to just generally help with technique. I wouldn't really say singing is something that can be taught (I don't think that people either can or can't sing either) but rather it is something that you have to learn how to do yourself. What could be good for you if you're starting out singing is firstly learning to sing in tune (it won't matter early on if you 'wobble' a bit on the notes but as long as you're hitting the right ones then it's fine). Sing along to your guitar or violin (much better than singing along to songs).
Once you can sing in tune, find out what your range is but bare in mind that singing far below your range and far above it can and will damage your voice. Singing falsetto is very different than singing high but falsetto is something that I'd suggest you learn later. Once you've established a rough range, either continue training yourself or find a teacher. It's been a while since I ever had a teacher but if they exist (which I'd assume they do) I'd recommend going for one that specialses in rock (or at least popular) music as the singing style differs greatly to classical. The technique will probably be better to be told face to face by a teacher so they can assess what you're doing wrong and tell you how to right it rather than you trying to find a work around on your own.
Finally, I really wouldn't recommend growling. It is very, very bad for your vocal chords.