The 'optionals' are just that. It's down to you, if you feel it needs them sorting.
You won't get the old crown back. Rolex do things on an exchange basis. Same goes for all of the other service parts too unless you fork out even more for the privilege of buying new, and that'd probably only apply to the insert. I stand to be corrected but I think that's how it goes.
Re the clasp, if it's really had it then, at that price I would be considering buying a complete new bracelet and then selling the old one for spares to mitigate the cost.
As with most things, it all depends how far you want to go with it. Anything Rolex tends to get expensive really quickly!