You can change the PICs oscillator to whatever you want. Microchip gives formulas for calculating baud rates given any oscillator frequency. PBP will work as well. The only problem is that any routine that uses software timing routines will be off. If you use DEFINE OSC 10, and you are actually running at 14.7456 Mhz, then PAUSE 100 will actually be a PAUSE 68 (it will pause for 68 mSec). Likewise, the SERIN/SEROUT routines will be off by the 10/14.7456 ratio. If you use SERIN2/SEROUT2, you can simply use the formulas given in the PBP manual to choose the correct value. If you use HSERIN/HSEROUT, you simply set BRG and the associated registers according to Microchip's formulas. You won't be able to DEFINE HSER BAUD !

Everything will work - if you take into account the new frequency.