How to unpack and edit boot.img for ROM porting?

I recently downloaded [this ROM](http://forum.xda-developers.com/showthread.php?t=2480246) for my Allview P5 (Allview P5 is the equivalent of Gionee GN700W/FLY IQ441/QMobile Noir A8). It`s called Primonex ROM and is made for the Gionee version of the phone. - Firstly, I tried to install it as it is but it got stuck at the boot screen. - After some research I found out that it could be a problem with the boot.img file and I don't know how to extract or edit it... Can someone tell me how to do it?