I've been playing around with MPLAB-X for a few days now and it appears to be a very usable IDE now, especially when compared to MPLAB. Unfortunately, installing a new compiler under MPLAB-X is not as easy (by a long way) as it was under MPLAB, but offers considerable advantages. You basically have to write a plugin for MPLAB-X using the MPLAB-X SDK.
http://www.opensource4pic.org/content/content/mplab-x-sdk-mplab-x-ide-230
If the above is not available, you can try here
http://www.firewing.info/downloads/sdk/
There is an example project and documentation in the above download that shows how to create a compiler plugin for MPLAB-X, so you would not be starting completely from scratch.
Is there anyone who could help out in this respect? If you can, or know anyone else who can, then please do get in touch...
