It sounds like you may need to make some shorter trips first. That way you'll get a feel for this. I assume this is a travel trailer? Do you have a heavy enough truck? What are the DOT dates on the tires? If they are over 5 years old, they need to be replaced regardless of what they look like.
We use a Garmin GPS, Google maps and sometimes Microsoft Streets and Trips to plan our trips. We travel only about 200 miles per day and stay around 60mph, but we have a diesel motorhome. If you are pulling a trailer you may need to go slower to avoid sway.
Again, I suggest a few trips much closer to home first.