I'd allow about half an hour. People say Da Michele is touristy but when I was there in October I was the only English speaking tourist at that time - so it depends - if you're there at lunch with five cruise ships in at the same time then it will be like downtown New York or London. Then again, you could get lucky. Thing is, the pizza is what makes it so sought after. It's one of the best in Naples and is in a convenient spot for you. You will have to wait - be prepared for that. You'll get a ticket and have to stand outside until called and they only serve two varieties - Margherita and Marinara (by the way, the marinara has no seafood - it is named that way because of the fishermen who would take it out on their boats as it had no cheese - just tomato sauce & olive oil).
As for 'safe' I wouldn't recommend walking to the station late at night - say after 10pm. It's a really run-down, seedy dive area and just unpleasant as it is also undergoing major construction for a new rail line, so it's also a mess. Easier to take a cab.
Edited: 9:57 pm, December 23, 2013