First thing to check would be whether the distance between the headrest posts are the same in the Gen1 and Gen2 Muranos (I would assume they probably are).
If they will physically fit, then you should be able to install them in your '07... I've just fitted the very same units to my '09 Murano and found that they can be installed without any real integration into the car - all they need is power, which you can tap from a power outlet/cigar lighter. (My kit came with an adapter to plug them into a power outlet, plus a FM transmitter which allows the sound to be picked up by your radio and played through your speakers).
The install instructions are here:
http://www.leeparts.com/pdf/999U8-CV000.pdf
It really is a very easy install (took me about an hour) and as long as the headrest posts are the right size and distance apart, they could be fitted in any car- the very same units (made by
Invision) are fitted in BMWs, Audi's etc.
Happy to help if you need any more info!