Since you have the diesel, you will be fine on power as long as you haven't put radically larger tires with no change in differential gearing.
At that much weight you should be using a proper hitch, not bumper pulling. If you have trailer brakes, make sure the brake controller is properly setup. Just give your hitch a good once over to make sure everything looks solid and not weakened due to rust.
If you have a manual, pull in 4th gear to minimize wear on the transmission, though some people say pulling in 5th is fine, it will put a bit of extra wear on transmission components.
If you have an automatic, make sure you have an additional transmission cooler installed. If once you get up to cruising speed (I drive 60 normally, but I wouldn't tow anything more than 2Klbs faster than that anyway) if it shifts in and out of overdrive more than once every 5-10 minutes, just turn off the overdrive. Otherwise added wear and premature failure will result.
Make sure the safety chains are free from major rust and are of a consistent thickness, you should adjust the ball receiver so it fits snugly on the ball, but should it come off, you need those chains to hold in order to prevent an accident or death behind you.
All lighting should be tested. All major components should be looked over, including the backside of tires on both the trailer and tow vehicle. Proper inflation on the trailer is critical, too low and the tire may overheat and blow out. Too high and the tire may fail due to heating and overpressure due to said heating. (follow the cold inflation pressure on the sidewall)
Make sure you are alert and aware of your surroundings while towing. In my experience, boats have a habit of rocking and swaying under hard braking, just give yourself some extra space.
Most everything is standard practice, you should be just fine. I only list everything because the one thing you forget, will be the one thing that goes wrong.
Good luck!