Yeah... Nothing about that is easy...
I wouldn't recommend building an RF transmitter/receiver yourself. RF is a specialty area and doing it right would require an oscilloscope, a frequency counter, and probably an RF spectrum analyzer and a signal generator. Just renting that kind of equipment would cost more than a good wireless mic set-up.
As far as digital signal processing, that's going to take a fairly high-power processor (assuming you want good audio quality) or a special-purpose DSP chip. If you've done some DSP before, that might not be a big deal. But if you haven't, you are probably looking at a few months of study. And, you might have to invest in a software/hardware development kit once you choose a processor.
Other than the mic preamp, building an ADC & DAC are probably the easiest part. But, I wouldn't say "easy"... So, you might look into that first. If you think you can handle that, you might look into the RF & DSP aspects.