Make sure that you change the oil before leaving. You will be working the 2.5 somewhat. 800 lb is not a significant weight to be towing with the 2.5 if it is manual but still needs fresh oil.
Key is to keep the RPM's up in the 3,000 to 3,500 range when you are pulling. You can readily run 70 in 4th gear with the 2.5/AX-5. That is where the torque is best. MUCH better to run at 3,500 RPM when pulling than at 2,000 RPM.
Check into if you can fit some kind of sway control onto the setup. To really help, you would need to get an equalizer hitch, but typically the 5x8 won't have the correct frame to set one up. But one of the friction bar types would be better than nothing. 75% of the issues in towing can be resolved with the right hitch setup.
The issue will be one of sway and tongue weight more than anything. The YJ is not set up in the back springs to carry the additional tongue weight. The 100 lb from that small a trailer isn't bad, but loading the back of the YJ with more STUFF (300-400 lb) adds to it. Keep the heavier stuff in the trailer and the lighter stuff in the vehicle. Nothing extra in the vehicle if possible.
Keep the hitch as short as possible. Every inch extra that the ball extends back behind the axle adds to the lever arm when the trailer wants to push you sideways. The YJ is short in that respect anyway and that helps when towing something larger, even with an equalizer hitch.
Check the drop on the hitch when weight is added. Measure to the hitch. Then stand on the hitch and see how much it drops the hitch. That is about what your trailer is going to do. Pump up and down on the hitch and see how it bounces. That, again, is about what the trailer is going to do as it goes over sharp swells.
Mileage wise you should be able to get about 12-14 mpg overall. My average towing the 29' self contained trailer was 11 mpg.
Make sure you switch out the flasher to a heavy duty one for trailer towing. Typically the standard one will flicker instead of flash if loaded down with trailer lights.
Again, keep ahead of the torque curve and get the RPM's up BEFORE you get into a lugging situation. You will be able to experiment some as you start out, but if you are running along at 65 or 70 and you are coming up to a decent sized incline, get it into 4th BEFORE it starts to slow down. Drive it like a truck and not a sedan with an automatic and kickdown.
You will likely run the trip about 30% in 4th gear and at 65 or 70. Good to get comfortable with it but don't get over confident and forget it is back there. It is necessary to drive it as a towing rig rather than just a single vehicle.