My wife and I have an idea that we want to patent. We think we have a unique idea and searching through patents hasn't turned up anything close (although I may not be searching correctly). The idea is based on combining existing technologies in an innovative way to make a useful product.
As an analogy for our idea, say the current state of the art is the really old school computers that have no monitor or mouse or anything, just a printer. I come up with the idea to add a television to the computer to give it a display. Say I also want to give the computer a power switch because right now you just plug and unplug the computer to turn it on and off. I am also going to add a mouse and speakers and internet access. All of these things exist independently(even the internet somehow without any computers currently hooked up to it) but until now they haven't been combined in one unit.

My questions:
1. Since each step is a unique idea, would you need to file seperate patents for each part? Say for instance that I try to patent the entire combination, does that entitle someone else to do bits and pieces of my idea without violating my patent?
2. in the example above, there are hundreds of ways of switching the computer on and off, but no one has ever done it before on a computer. How specific would I need to be on the mechanism for doing so? There is commercial technology out there to perform the function in several ways but the idea itself is unique, do I need to list as many ways to perform the function as I can find or is it enough to patent one or a few ways to perform the function?
3. At what point do I need to hire a patent attourney?
4. What are the advantages of filing a provisional patent versus filing a non provisional application?
5. How much money does the idea need to generate to justify hiring a patent attourney? I know this can very greatly but any rough ideas of the costs associated with hiring a patent attourney and filing for a patent would be greatly appreciated.

I think that's all my questions for now. Thanks in advance.