I'm a complete newbie. I know you're supposed to sing from the diaphragm (heck, I don't even know if I'm doing that right!) and thats about it. I have trouble matching pitches, my voice is out of control really haha. It's something I've always wanted to learn. I have a piano, so I figured matching pitches with that would be a good start to figure out what my range is.

Anyone have any tips, websites or youtube channels they would recommend to get me started?

The vocal style I want to be able to sing is like La Dispute, Touche Amore and that whole genre, that kind of yelling vocal style But I figure I should learn to walk before I run.
Smart call learning to walk before you run. I'm not huge into those bands but I've listened to La Dispute and it's very harsh yelling vocals. There shouldn't be any permanent vocal damage if the technique is done correctly to achieve their sounds but it still is taxing on your throat since constant belting requires a lot of muscle control from your throat. It'll be very hard to sing this style when you're experienced, let alone as a beginner.

I have no recommendations for YT channels, manuals or anything of the sort. My strongest recommendation, and anybody who sings will tell you this, get a vocal coach. There's a lot of self doubt about whether you're doing things correctly when it comes to singing as it's not like other instruments where you can clearly see your mistakes... It's tough to know whether you're doing something healthy or whether you're doing something damaging to your vocal cords, and a teacher can help you with this, as well as give you instant and direct feedback on the specifics of your singing.

Singing from the diaphragm basically means good air support, when you breathe in, your stomach area should be moving up (looking like you're fat), you keep the air in there and when you sing, you should be pulling your stomach inwards and pushing up from the stomach to get a controlled release of air into your throat. I know this explanation is kind of confusing but this is why you should get a coach haha, it's much easier to explain in person.