If the fan is running you should be able to hear it if you put your ear to the out vent. You would also be able to feel the fan running there or at least make a piece of tissue paper show that air is moving. No fan will make a laptop overheat pretty quickly and could cause real damage. When you used the vacuum did you somehow unplug the fan. Can you run the laptop with the fan exposed to see whether it is running? Replacing the fan module is not a massive job but if you cook the heatsink and paste that transfers heat to the fan veins then you are looking at plenty work.