Towing / Gear advice?

I have an '02 Dodge Dakota 4x4 quad-cab w/4.7 auto, 3.55 gear. tow and hvy dty package ordered from factory. My owners manual states 4750lb max tow capacity with the 3.55 gears. I just bought a camping trailer that is 4620lb dry and will probably put 3 -4 hundred lbs inside, so rounded off to 5000lb. I only camp about 8 times per year and except for one trip through western MA to the Big E, (I live in eastern MA) the trips are all local (within 50 miles and small hills). I have only towed it once, from the dealer to home (15 miles hwy). Off the hwy it had a lot of get-up-and-go. It did ok hwy but the slight grades slowed me from 62mph to 51 w/cruise control on, (I put cruise on to see what the transmission would do as far as shifting) but it did not shift down.  I had OD off of course. It does seem that the wind drag was most of the issue slowing me. My rpm was about 2500 and my most efficient torque is made at 3200rpm.
Please note: I am not about to tow with a vehicle that cannot handle the load structurally. This truck has a rating of 5850lb with 3.92 and 6400lb with 4.10 . I just want  only what is absolutely necessary for modifications.  That is why I would appreciate some advice from someone with similar or closely related experience.
I am hoping to find others with some experience to share.
Questions are:
Will superchip tuner help enough?
Should I go with 3.92 or 4.10 gears if gears are the way to go?
How much effect do those gears have on fuel mileage?
My Local dealer wants $1860 to change the gears. The truck is still in warranty (xtnded) for another 1 1/2 yrs so I don't want to have anyone else do the work if I do change gears.
Please help with any info you have.
Thanks
Pete

I think the biggest problem you face is the potential liability.  If you have an accident while towing a 5000 lb trailer with a truck that you knew was only rated for 4750 lbs, then the lawyers will shred you to pieces in front of a jury.  It's sad that we live in such a litiguous society, but we do...

I would highly advise the gear change.  And go with the 4.10's.  This will help you much more than a chip will.  On my F-250, the change in gears had very little effect on the gas mileage.  Do the gears, you will not regret it.

Gears are the answer, but you may need to beef up the rear axle suspension as well. Be sure to weigh the rig axle by axle and check the truck rear axle GAWR and also max tire loading. The 3.92 should be sufficient, I think.  Another option is to add a Gear Vendors Over/Under Drive (auxiliary transmission). That way you simply get more gears, without any penalty on fuel economy. Will cost more than a gear change, though.  Gear Vendors

I suspect your 4620 dry weight is the  usual optimistic value from a sales brochure.  They are almost always on the low side for any given trailer,  so get that trailer weighed right away and find out what you are really dealing with. Also, remember that the trucks tow rating is given with only fuel and driver onboard - doesn't even count a hitch! So the actual tow capacity is somewhat less than the max, especially if you have passengers onboard.

Is this a fifth wheel or travel trailer?.

Will superchip tuner help enough?

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No.

Should I go with 3.92 or 4.10 gears if gears are the way to go?

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Yes, go with the 4.10.  But only if you are sure that  the rating for the 4.10 rear end machine is for the otherwise identical model -- as opposed to going from a 1500 to a 2500.  You want to be sure that the brakes, tranny, drive train, and frame and suspension can handle the weight.   

How much effect do those gears have on fuel mileage?

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Your mileage will go into the toilet.  So?

My Local dealer wants $1860 to change the gears. The truck is still in warranty (xtnded) for another 1 1/2 yrs so I don't want to have anyone else do the work if I do change gears.

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Well as another has said, a Gear Vendors box would be a good alternative and should not affect warranties.  $1800 woulld be a close swap in price.  Anyway I would price it.  It would have some advantages in unladen gas mileage.  BTW, forget towing with OD engaged.  Lock it out.

We constantly recommend that folks use the Gross Vehicle Weight Rating (GVWR) to evaluate towabillity.  It is a number that can be found on the DOT plate on all trailers.  Dry weight is more of a come on than a useful number.  If you load 300-500 lbs of gear in your trailer, you will be the first in trailering history to go that light.  40 gallons of water alone will tip the scales at 320 lbs.

I have an 02 Dakota Quad Cab with the 4.7L 4x4 and the auto.  It has 3.92 gears in it and I get around 17-18 MPG with highway and city driving so I would expect to get something around there.  As far as gears, its about $500 an axle to do a gear swap that includes the purchase of the gears, but you could go cheaper and get some gears out of a junk yard Dakota.  I pull a boat that weighs in at about 4500 pounds and the 4.7 pulls it along nicely.  There are some big hills that will slow me down but I can usually hold it around 55.  Its no big block but it will pull a fairly heavy load and do a good job.  I really doubt your mileage will be effected that much by a gear swap. By the way that heavy duty package is awesome on the truck.  I have pulled 10 mile long 6-7% grade with a 3000 pound utility trailer while its 100 degrees out and the aux cooler and heavy duty fan keep it nice and cool.  Once that temp guage makes it to about the half mark my fan kicks on (you cant miss it it sounds like a dump truck) and you can watch the temp guage drop back to normal.  They are good trucks and good luck