We have a 2007 Pilot EXL and considering adding a hitch to tow a 4x8 trailer. Nothing heavy, just some brush and firewood. The dealer wants to add power steering cooler & transmission cooler for over $1200. Our questions are: Do we really need them or can we just get an after market hitch for less than $500. Will the addition of the two coolers affect MPG when not towing?
The dealer is NUTS, and greedy. You MAY need a transmission cooler if you tow some weight for any distance, but a power steering fluid cooler???
A good transmission shop can install a cooler for about $80 for the part and about $100 labor. I personally have installed 6 of these over the years. It’s a 1 hour job at most.
Go aftermarket. Dealers know very ittle about these things.
The dealer is doing due diligence as he has no idea what you really will be towing. The parts he wants to add are great additions for your car and would be done much cheaper by yourself or a qualified indie. They are good additions for your car. No they will not detriment gas mileage.
Everybody comes in saying they’re only going to haul feathers and end up hauling rocks sooner or later. 
Firewood, in the true sense, is not a light load. So, as mentioned, the dealer errs on the safe side and installs the factory tow package parts. You can do half the job now and hope you never need to haul more or just go ahead and put in the full package and never have to worry about if you’re taxing the vehicle…
I’d definitely do the tranny cooler, call around like Doc says. Towing can be very hard on the transmission, and that’s BIG $$. Not sure why power steering cooler would be an option. Neither would hurt mileage.
Look around the web for how to install a transmission cooler. You’ll be shocked at how easy it is and will likely be very aggravated with the dealer. This doesn’t necessarily mean that you’d want to do it yourself (though you probably could) - its just that, as Docnick said “The dealer is NUTS, and greedy.”
When you consider the additional $1,700 you are considering spending, perhaps you would be better off with a an old $500 beater truck for such duty.
I don’t see why you would need a power steering fluid cooler, but a transmission cooler is a necessity if you want to preserve your transmission. Of course, you don’t have to have this work done at a dealership. Any reputable shop can install a transmission cooler for you.
The dealer wants to make money. For the use you describe, it’s well within the standard tow rating of 3500 lbs of a Pilot. The Pilot is much more substantial than you think and can handle occasional towing that’s “nothing heavy” of up to that weight with ease.
You don’t need anything other than a hitch for utility trailor towing. Find me a standard 4 by 8 utility trailer that can handle as much as 3K lbs anyway.