I have done a few projects that required getting on a plane or driving more than a few hours to get to the job site.
Having someone local can be a big benefit.

One of my first out of town projects was across the country.
We were given drawings, which we marked up for screens, projector, wire and power etc.
As it was commercial, the GC ran pipe to locations and it was up to us to pull our own wire and deal with the rest. We asked that there be tall ladders available to us as these would be expensive to try to bring with us.
We staged the system and programmed in house (AMX), boxed it all up and shipped. Found local distribution for wire so we could buy and take to site when we arrived.
Myself and 1 tech, flight, hotels, car rental and meals paid for plus a daily rate that was higher than our normal rate as we knew we would be working late to complete within the few days we allocated.
The key is to charge a daily rate that is worth your while, and figure out a per diem that does not require you to eat 3 meals a day at McD's.
Be organized and whatever time you think it should take to do the work, at a minimum double it. You will get there and have to meet with people who could take 1/2 a day just talking to you before you get any work done. You could face traffic delays you are not used to and getting from your hotel to site could take up an hour each way you had not accounted for. Tons of things we encounter on jobs that burn time can and will happen.
Test equipment before you send it (and add this time to the bill). Get programming (or most of it) done before you leave.
If you have a rack going to site, and you have another at the shop, layout the equpment and pre make and label your cables if you can, anything that can save time on site will be helpfull.