I'm sorry to say but, yes, you should pull out the dryer and apply the de-oxidizing compound. Aluminum will oxidize without it. Over time, exposed to the oxygen in the air, it will form a white powder over the conductors which will cause the electrical connection to degrade. This in turn will cause resistance at the termination to increase which will cause your worst enemy, heat. Aluminum has a higher coefficient of expansion than copper. As the termination heats and cools, the problem will continue to get worse. Eventually there will be a failure. As Mark suggests you should check the receptacle for an AL / CU marking. I would expect that it will be all right. A UL listed receptacle will almost certainly have this. Also to stay within NEC guidelines you MUST use UL listed components. Lastly, please, go get the correct breaker. It is the one component that guards the rest of the system and places it in compliance with the code.