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.