The RNG150 uses the XMP protocol. Among remotes made by Universal Electronics, which includes Comcast and higher end Vizo, the setup code is Cable 1982. However, the Vizio VUR8 and URC-66700 don't have this code. Maybe a newer Vizio remote (e.g. the VUR9) does have it. If you try to enter Cable 1982, and you get two blinks, then the remote has the code. Otherwise, you either need to 1) use the Comcast remote, or 2) get a JP1 cable and upload the XMP protocol, or 3) buy a universal.
Besides the Comcast, the RCA RCRP05B ($20 at Best Buy and maybe Walgreens) or OneForAll URC-8820N or 10820N (Sears, but make sure the suffiz is N and not B00) have C1982.
If you want to use the Comcast and have it operate the Vizio, the setup code 11758. You can add in discrete codes (if your TV model supports them) using the data and procedures on page two of the Vizio discrete thread
. Make sure you prepend two zeros to the 3 digt EFCs to make up the 5 digit EFCs that the Comcast remote requires.