No to service contracts.
The service contract company is not in business to lose money and as stated above the commission to the selling dealer could be up to 50%.
As to buying online how will you get the rig checked out before paying?
So let us say you find a rig and you like it. You drive 700 miles to check out the rig and buy it. ARE YOU WILLING to walk away from the rig if it does not function perfectly or hang around a week while it is repaired? The predelivery inspection BEFORE PAYMENT will be most important. How will you get the engine, chassis and suspension etc checked before signing on the dotted line? Will a short test drive be enough? NOT FOR ME.