Well if your up for it realy depends on the complexity of your idea.
I would recomend going with C#. Its a nice language

To start Microsoft has lots of guides and tutorials that include the basic SDK installations.
You will need Visual Studio IDE, then the WP 7.1 SDK.
Having those two things installed is pritty much it, you can start coding right away.
Since its not a game your making you will be using Silverlight. Much of the UI building can be done with no coding at all, just placing componets! Their function however you will need to program.
I recomend you start easy by reading a few tutorials and going through the source code.
Once you've done that I strongly recomend that any questions you have, you post them at AppHub forum. You can try posting them here as well it woun't hurt !
For testing your app you can use the emulator that is built in the SDK. Offcourse you can also try the app on your phone once you have it developer unlocked.
You can even debug the app on the phone at runtime as long as your phone stays connected to the PC while debuging.
I wish you the very best of luck and I will folow this thread if you have any more questions.
P.S.
If your more of a visual guy you can look at the video tutorials like
Tutorial: Developing a Windows Phone 7 Application in 25 Minutes - YouTube