The H&G kit comes with a hard surface gadget that will maintain the span/spread but I would probably do something with small chain. The biggest issue is the tripod has sharp pointed legs (so a surveyor can stick them in the dirt). They are removable. Maybe some rubber cane tips could be put on the legs. The slimline is top heavy. The tripod has an eyelet below the mast. I have been filling a five gallon bucket with water and using a bungee to tie it to that for ballast.
If your Expedition has a roof rack I'd consider using that. Maybe you could use two crosswise 2x4's with two holes in one and one the other to accept the tripod's tips. Just bungee them down. I'd get all laid out at home and maybe even tied on before you go. Then just pop in the tripod and level it and take your shot at the 101. Preset the Elevation and Tilt before hauling the dish to the roof. You will be slowed down by taking a fresh shot with the dish rather than the tripod each time. Be careful 5 degrees off can make you hit the wrong sat but with your receiver and set on and a the Signal Strength Bar(s) page you should be able to see the 101 pretty quickly.
I would also get the HD Folding LNB Arm Kit to make the dish more stow-able (requires hack-sawing, drilling four holes, and small fingers). The hokey compass, bubble level, and Sat Finder meter that come with the Combo Kit are actually quite functional tools and he ain't overcharging for them.
I have some concern as to whether you bought a multi-switch or SWM LNB dish. The SWM dish requires a power inserter while the older multi-switch require B-Band converters. Just make sure you have the right gizmos inline.