Hi There,
Let me just start by saying that I am probably older than most folks here. I have gray hair and wear bi-focals.
We tow a 26 ft ultralight travel trailer with an 06 DC 4x4 and I'll be honest I would not want to tow anything larger. Our "wet" weight is about 9800 lbs combined for a normal trip. GCVW for the Taco with tow package is 11,100. We have pulled some long 7% grades with this rig. We aren't the first one up the mountain but we aren't last either. I tow in 4th gear, the engine purrs along at about 2700 rpm at 62 - 65 mph.
With a "dry weight" of 3500 lbs your tongue weight should be at least 350 lbs. This will put the truck on the bump stops. You will want to invest in either Timbrens or Super Springs. I chose Super Springs for my needs.
Your dry weight does not include any accesories. Propane, a/c, microwave, tv etc. Before you load the first quad on there you will probably weigh closer to 4000 lbs. Gives you 2500 lbs to work with. Add fuel for the quads, fresh water, food, drinks, clothes etc and it adds up quick.
Towing a 6000 lb vehicle on a trailer is different than towing a travel trailer. Granted, weight is weight but a travel trailer has more frontal and sail area and this makes a difference with head and cross winds.
One last word of advice, invest in a good brake controller and a weight distribution hitch with anti-sway. That one time you have to make a panic stop on the interstate you will be glad you did.
Will your truck do it? Yes but you want to do everything you can to make sure that not only you but those around you on the road are safe. Getting the load moving is not such a big deal. You want to be able to control it and stop it safely.
Ask the seller if you can hitch up and tow the rig somewhere and get it weighed with your truck.
Off my soapbox now.
Enjoy your truck and your new rv.
Chris