the prewire from what ive seen on other units means just that. the wire is run though the trailer and up into the roof, but they do not run it through the roof. They leave the wire laying inside the roof and have the roof marked with the location to drill to find the wire.
If you cant find the location to pop a hole in the roof before the satellite tech gets there. Just have him run a temporary line through the door or a window (if your unit doesnt have any other satellite/cable jacks in one of the compartments), that way he can at least get it functional and know everything is working. Then when the location is found, the satellite can be wired properly without having to hack up your roof.
'14 XLR 395AMP
'16 Ram 3500 DRW, 6.7 cummins w/aisin trans and 4.10 gears