That's awesome. If brakes have any pitting in the bores from moisture you may consider having them sleeved with stainless, they'll outlast you. And of course all lines as already said. With that low a mileage with some tlc I'll bet it'll be running great in no time.
For the siren take her apart and I'll bet you'll be able to lubricate and clean it up enough to work, also check all contacts for the front light while your there, it often had a flasher for it. The rotating light might also just need clean up, but a small replacement motor can be had if needed as well.
