are you overreacting? no signs on truck? empty building (how do you know it is empty?) i don't know what is going on exactly but unless you decide to go with your own services elsewhere you have GS insurance and they are willing to help.
since you have been having the mechanic working on your rig you should by now have some sense on his ability.
and finally, you really don't have to stay with the rig you can always go to a motel.
here is one shop: http://www.rvrescue.net/
again, remember, you do not have to use GS you can always pay for it yourself.