Hello GSX,
If your buying a new HDD and Operating System, you probably better starting from scratch. Put your new HDD in as your master HDD and the one you currently have as slave. Once Vista is installed, you will see all your files and everything you need as another drive in My Computer.
I'm assuming you currently have an IDE HDD installed at the moment. IDE HDD's have 40 or 80pin ribbon cables attached to connect to the motherboard. SATA normally have a thin red cable instead. SATA is faster, but you will need to make sure your motherboard supports SATA, it will have a SATA socket demonstrated here:
I'm not you need to worry about RAID here. RAID is not a type of HDD, but more a method of storing data on two or more HDD's. If for example, your worried about losing your data, you can have two HDD's which are "Mirrored", and when you save a document to one, it is also saved to the other. If one HDD fails, then you have a backup on the other.