I'd be very cautious of putting chains on the front of the pathfinder, they can easily foul the suspension and that could get really expensive, not to mention potentially cause a nasty occurance.
I'd look at the cost of dedicated snow tyres and the likelyhood you will revisit this area.. if its a one off then a pair of chains that you could sell once the trip is over would make sense.
I have quite alot of experience in driving snow and compacted snow/ice, the key is to keep the speed down. Treat all the surfaces as ice and you won't go far wrong. A pathfinder on a slide will take some stopping, and shouldn't be mistaken for drifting where you still have a relative amount of control.. on ice.. once your gone... your gone. ABS and traction control will help but they can't replace good old caution and application of common sense.
Take a look on youtube for videos, be lots out there including the bumps.
If you do need tyres anyway then the compromise would be AT's.. though you will have a drop in economy compared to purely road biased tyres.
I know that the use of chains on the rear only would be likely to cause theoretical problems in the difference in rolling radius and the use of 4x4... but couple this with the fact your using them only on some of the most trecherous and slippery conditions and then you remove the likelyhood of locking up the drivetrain and any damage.. clearly you wouln't use the chains any further than is absolutely necessary.
I have a set of chains that are used on my 7.50 r 16 Landrover tyres and they fit great on the pathfinder. Military surplus on ebay
Also look up snow socks on youtube.. they are awesome.. much lighter than chains and you could run them on all 4 tyres with a great reduction on the likelyhood of damage at the front end.