head gasket

but if he's just taking it off to look at it he should be fine.but if he does work then yes you will have to get new ones.but blasterman312 has a good point.you should always pay attention to the condition of them
 
Once a gasket is installed and the engine ran until hot the gasket should not be re-used in that condition. You can take a touch, heat it up till it is all red then drop into a bucket of water to soften the temper and it can be re-used at that time.

Would I do that on my bike? No, gaskets and oil are too cheap for me to re-use.