As nobody answered, MPLAB ceased development over a year ago at version 8.92. MPLABX is it's replacement and is still the current release of IDE. Unlike 8.92 which is for Windows only, MPLABX is cross platform.
Within MPLABX you can install almost any compiler you want but the best ones for continued support from Microchip are the ones they produce themselves. They are called XC8, XC16 and XC32. All have free versions and 'pro' versions for which you have to pay a fee.
The best compiler supporting virtually all the PIC12, PIC16 and PIC18 series in one program, with an IDE, simulator and full debugging capability is probably WIZ-C which is not free but is lower cost than most other compilers. It can also simulate and simultaneously debug in a virtual environment where several PICs are interconnected. For example, you could simulate a system with several different PICs, each running their own programs and joined together by I2C or UART links.
Brian.