8000lbs is pushing it on stock gears. If the tongue weight of the trailer is above 500-600lbs, which i'm guessing it is, you are going to want to beef up the rear suspension. Forget helper springs unless you dont mind it sagging 4-6 inches while loaded. I would go with an add a leaf kit or replace the rear leafs all together with a pack that has an additional leaf. Might as well do the shocks too, they aren't that expensive for what you're looking at.
I cant remember what the stock gears are, either 3.55 or 3.73 however jumping to the next ratio will give put a bit more torque to the wheels, however your gas mileage will slightly decrease (about 1mpg) and your rpms at a given speed will also increase, as well as your speedometer saying that you're going faster than you actually are.
A lot depends on the tires you are running, the larger the tire, the worse it tows, to an extent.
As for the other things you can do, check for the deathflash. There will be a sticker on the PCM on the passenger side firewall that says something like "factory authorized update". There are guides to fix that problem under the plenum gasket thread in the Engines section.
Only other things I can think of are a nice set of brake pads and a tongue at the right angle.