First, you need to decide what transmitter and receiver you will use. AM? FM? If AM, superheterodyne or superregenerative receiver? What range is required? Outdoors? Indoors? What's the biggest number you will send? What's the biggest number you are willing to spend on hardware?

Second, the RF receiver power use will likely dwarf the 12F629 power use so your sleep idea is probably not worth pursuing unless you also plan to power down the receiver while the PIC sleeps. How frequent are the transmissions?

I think SerOut/SerIn overly complicates this type of communication. Check this recent thread for ideas.