Choosing the Right Controller for AD Signals Processing

Hello, I'm recently became interested into microcontrollers, so I do not know much about it. I was looking for something like a board that has easy interfacing the computer and that allows me to do some nice calculations with signals. I want to make something that does the following: 1) I have a black box from which I can only get 4 analog signal at a rate of 10us ( this signals are my inputs ). 2) I need to read those inputs and change then to digital ( basically, I need to have ADC -- i know what it is but do not know how to work it yet ) 3) After I get my signals ready, I need to do all kinds of processing: frequencies, energy, stability, etc... THE HARDEST PART 4) Make a GUI that allows the users to get the inputs just by connecting the 4 cables giving the analog signals, click a button and get the results. ( i.e the default calculator in the computers accessories folder ) Can any one give me any comments? any recommendations of what to buy? can i execute anything programmed in your recommendation from an intefaceable code made in c#? If so, how can I link them? I will really appreciate your help.