You'll want a cotter press if you want to service the BB. You can either buy the BikeSmith one or make your own out of a Harbor Freight Chain tool for under $20. Using the hammer method is just a PITA and too many headaches when you can make a decent one that turns the chore into a joy. I can pull out a cottered crank with the HF tool faster than I can thread in and remove a square-taper crank with the proper tool.

Also remember the fasteners are neither Metric nor SAE, but Whitworth. Use whatever/whichever fits the best and be careful and you will be OK.