I looked on Park Tool, it seems when you a buy new Crank Set you get all of the parts you need to fit it - is this correct ? I thought the BB was a different component fm the Crank Set....
First, you need tools to get the old crank off. Most new cranks come with the chainrings mounted and include the bolts needed to fasten them to the bottom bracket spindle. Bottom brackets are bought separately and don't come with the crank. Some of the newer design Shimano cranks come with the spindle built-in but you have to buy the bearing assemblies separately.
BTW, look inside one of your current crank arms. There should be a model number stamped there so we can be more helpful as to what tools you will need.