New Z315E owner , rookie questions

Hey all. I just had my first JD mower delivered. It’s a 42” Z315E,and I also picked up the cutting deck mulch cover. I had 3 rookie questions #1 Would it be better to wait to use the discharge cover before installing mulch blades ? #2 is it worth getting the entire “mulching package” including the plastic hardware for under the deck, or would just mulching blades and the discharge cover be ok ? #3 Does the risk of rust outweigh to e benefit of using the hose attachment to clean the underside if the cutting deck after every use Thanks