Jack,
If the wheel you can't spin by hand is at least free enough to allow the truck to roll, all hope is not lost.
I would suggest generous fluid application and gentle persuasion, giving some time for the fluid to migrate inside and hopefully work it's magic.
You may also need to try and give those bolt heads a few raps with a hammer as strikes could cause rust to break free and allow for movement again.
Hopefully some useful suggestions to help the process.
Dan
