Microcontroller Wireless ECG (need help in MCU)

Hi,

i doing a project of ECG and wireless Transmission.

Sensor Design Considerations
•Capability to sense low amplitude signals in the rane of 0.05 - 10mV
•Very high input impedance, >5 Mega-ohms
•Very low input leakage current, < 1 micro-Amp
•Flat frequency response of 0.05 - 150 Hz
•High Common Mode Rejection Ratio

I need to do Analogue to Digital Conversion before sending to wireless Transmission Module.
My question how to choose my microcontroller?
how many bit of ADC and channels is needed?

thanx in advance
Regard's

how to see MCU memory is enough for the device ?