i cant see a problem with doing that as long as the camera you use has the correct outputs.
Another wireless is probably suggested as it can get complicated unless you can find a dual channel transmitter/reciever combo?
Also, with different wireless units they both only have to be one way.
With the convertions for the pc to record, you might be able to find a cheap pc capture card from an online store like dealextreme or ebay.
As for the third question, if you have spare pins and space on the mcu for the code, it could be done, but a smaller seperate microcontroller like an
attiny/atmega might be better suited to performing the task on its own.