I have a computer running 2x250gb hard drives, and I'm quickly running out of space on them.  I was thinking of adding another drive to expand my space.  I found a 750gb hard drive on sale for today only, and was about to buy it, but realized that I think I'm running raid 0, and I don't think I can add a bigger drive than the others with 0.  
 
I'm kinda a newb, but I'm good at reading instructions and figuring things out.  
 
Here is what I would love to know:
 
1. Can I add a 750 HDD to my current system, and how...
2. How can I find out what RAID I am currently running.  
3. Any suggestions for installing it, since I haven't done one before.  I don't want to format my other drives because they are full of data I would like to keep.  

You can add it, but you can't add it to your RAID array. It should show up as a separate 750GB volume. You should just be able to plug it in, format, and go.