Ive been playing the violin for over 18 years now and I am an expert, Are there any tips or things you would like to know about it? 
Wow that's a long time. I really wouldn't even know where to begin with that, it seems so complicated. 
Its not complicated,Since its the smallest and highest-pitched instrument it makes it very easy to use and learn, With regular practice you can learn how to use it in no time.
I do know how to play a little guitar. Is it similar? The thing that gets me is the bow
Its kinda similiar, violins have a hollow wooden body just like a guitar and have the same resonating chamber. 
How does using the bow work?
Well I use a fiddle bow on mine and its pretty easy, you just wax up the string on the violin and rub it gently on the strings to create the sound. 
That's cool, I would want to give it a try one day. It makes such beautiful music