Depending on left or right you will first need a crank puller to remove the crank in order to replace it. You will be better off taking it to a bicycle repair shop. Cranks usually only come in sets but the shop may have a spare or they might be able to order you a seperate one. The same applies for pedals. If the threads in the crank are not too damaged you might just need a new set of pedals or one replacement. Hope this helps.