I don't know if I'd say 15 minutes, maybe 20 of you have to move the propane rack a little. If you can change the brakes on your truck, you can set up the WD system.
Seriously, It's not a real difficult job. You need to have an area large enough to have everything flat.
The main obstacle I see is this: If you need the WD to drive the trailer off the lot, that means you have to set it up at the dealer. I don't if they will allow you to do that.
If you can drive it off the lot without the WD to your house or nearby parking lot to do the work, you can do the work outside the dealer's lot.
If you can't make either one of those options work, then you probably will have to pay the dealer.