The particular brand of GMRS radio that you have (I assume you meant to type BTECH) is not an item Ham Radio Outlet sells, so we would likely be unable to program it for you. A quick Google search suggests that it can be programmed using the CHIRP software (https://bit.ly/35DWuDd). A review of this radio says it comes pre-programmed from the factory, however.
Generally speaking an antenna is tuned, not the radio. If you are speaking of modifications to power output or call frequencies ensure you are within FCC guidelines. Also, remember, with a few exceptions, you must be licensed to transmit on a GMRS radio. If what you are asking for is within FCC guidelines HRO may very well have the technicians to do it. If it is not , I highly doubt they will do the modifications.
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