Thought I would update this with information I have found.
I eventually received a call from Palomino but after having opened things up to try and resolve the fan noise. It turns out they use the Dometic after market fan kit but do not install the switch for liability reasons. They were helpful in determining why the fan was reinstalled incorrectly by the dealer and the location of J2 on the control board. They are also helping to setup some other repairs I won't do myself at another dealer. So all in all things seem to have turned around.
First the location of the inline fuse for the fan in my trailer is in the lower left hand side of the refrigerator. To remove it requires disconnecting connector J2 in the control box and threading to the front to gain access. If you have small hands this might not be necessary. Pics of the control box and lower end of fuse holder follow.
Here is what I found when I opened the upper refrigerator vent. It turns out the fan was reinstalled by the dealer and NOT Palomino. Not only does the hack job make the fan noisier but the straps attaching to the lines risk damaging them and causing leaks. I reinstalled the fan correctly using rubber grommets but is was still too noisy for me so I have ordered a different brand and will report on it after I've had a chance to use it. I've also installed a fan switch inside the trailer so we can turn it off while traveling and at night.
The fan specs are 12VDC 120mmX120MMX38MM at 105 CFM. I went ahead and ordered a thinner model so I can also isolate the fan from the factory mounts.