I do not use crystals so I can not comment on that.
Here are the configs to run at 48 MHz with a 4 MHz resonator.
Code:
DEFINE OSC 48
    @ __CONFIG   _CONFIG1L, _PLLDIV_1_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L
    @ __CONFIG   _CONFIG1H, _FOSC_HSPLL_HS_1H
    @ __CONFIG   _CONFIG2H, _WDT_OFF_2H & _WDTPS_512_2H
    @ __CONFIG   _CONFIG2L, _PWRT_ON_2L & _VREGEN_ON_2L
    @ __CONFIG   _CONFIG3H, _PBADEN_OFF_3H & _MCLRE_OFF_3H
    @ __CONFIG   _CONFIG4L, _LVP_OFF_4L & _XINST_OFF_4L