@JonasB,
I can't speak for the event but usually the Middle to High Scale trails (5-10) fill up fast with the lower rated trails having some room...
I am headed down Wednesday night I can check whats open and post up if that helps, but I am betting they can find you a trail.
Which trail sounds good to you?
If I were running my daily driver that needed to take me 300 miles home and it was my first time wheeling in Sand Hallow, I would probably looking at trails 1-3, maybe 4 if it sounds fun/extra appealing. Go, have a good time, keep your rig in the same shape you brought it and get your feet wet for the next time.
Don't be too concerned that most of the vehicles aren't full sized rigs (Trucks), you will see a ton of Jeeps and smaller type set ups... You will need to figure out a flag for your rig though.