Will i have to trim up the internal osc to get the boodloader to recognize the serial programming.
The internal oscillator only runs at 8MHz, which doesn't quite support 115200. So you can either program a new bootloader modified for 8MHz and 57600bps, OR you can use the standard 16MHz bootloader at 8MHz by configuring boards.txt to run at 57600 instead of 115200.
The oscillator is "precision" when calibrated. It should be good enough for serial communications, but it would be chancy if the calibration byte were erased or misconfigured.