They wouldn't have been able to drive the truck after 100 years for several reasons. The gasoline in the truck would have evaporated or broken down to the point uselessness. The oil would probably dry up and be hardened also. The truck's battery would have gone flat within months, due to degradation. The tires on the truck, if not rotted away, would surely have been completely flat and useless.
When the men wake from their sleep, they must release the latch that made the glass cases airtight, but the third one who wakes, Brooks, clearly just wakes up and pushes the lid up without releasing any latch.
When the gang pushes the rock that was in front of the cave, a track can be seen that it moves on.