You may get different responses to your questions, depending on who you ask.
>What is the best whelping box and how big does it need to be for a [large breed]?
If you are going to have very infrequent litters, I think it's best to get a disposable box. There is then no dismantling of box and disinfecting of everything before storage needed. You just throw it out. If you are going to breed regularly, you might want to invest in a more durable box.
There will be information about which size box to get on the manufacturer's website, you may need to measure your bitch.
>I want to put a webcam into the room so I can keep an eye on the puppies without disturbing them too much over the first few weeks. Has anyone done this and have a camera they would recommend?
You should be sleeping right by the box for the first 2-3 weeks of life of your puppies, so there shouldn't be much need of a camera during this time. You WANT to be 'disturbing' them, too - you need to be handling them daily, taking them out of the box, weighing them - you should not be worried at all about disturbing them, they need to receive contact from humans frequently.
If you need to monitor them whilst taking a shower, going to the loo etc - any webcam works very well.
>What else do I need?
Am awful lot else! Towels and disposable whelping pads, thermometer, lubricant, Dopram 5, latex gloves, newspaper, bulb syringe, bottles in case you need to feed and formula, ID collars, weighing scales.... loads more besides.
>What should I give her during labour? I read vanilla ice cream is good for keeping their energy levels up.
Calcium - but only after the first puppy is out. From that point on, it will help reduce the risk of eclampsia. You can buy calcium in syringes which can be squirted into the bitch's mouth during whelping. Besides that, some good quality wet dog food with a high meat content that you can add some powdered glucose to if necessary... (can also add that to water).