Im looking to set up a dual battery on a 05 Nissan Navara for a trip to Lakefield national park. I have been all over town and asked all the 4x4 stores, battery stores and had a talk with an auto electrician. They all have given me different ways of doing it, with parts and labour for them to do it ranging from $800-1200. I think i will try it myself.

What i need it for... to run waeco cf-50 car fridge average power consumption 0.86 amps/hr at 32degrees ambient temp.
Setup: i want to put the auxiliary battery and fridge in the tray body of the dual cab ute, run the cable down along the chassis and up to the vehicles battery.
The cheapest prices i got were $300 - 100 amp/hr glass mat battery
$149- dual battery kit with solanoid
$90- battery box with fuse

QUESTIONS:
If i buy this gear will it do the job?
Is it safe for the vehicles electrics?
Do i need anything other then what i mentioned?
Also, if anyone knows will the auxiliary battery last, in lake field we will be moving campsite about four times in five days on our way to cook town. with only 50- 100kms of travel a day to the next campsite. Will that charge the battery enough to make the five day trip, and if not what do i need to do this?


Hope this is enough info, any help appreciated