DSP circuits are quite simple. But DSP programming is not. While one may say that DSP is just another type of processor and some of them have C compilers and tools available (not free!), the digital processing usually requires advanced algorithms - otherwise it makes no sense anyway.. This is a job for a pro.
I was looking at similar projects myself,but it is exrtremly difficult to make anything yourself in digital as the ic does most of the work and you will not find information on those.You might look at PC radio cards,they are the best recievers going but they are not cheap.