roasting a whole duck

Whatever recipe you choose, save the fat !
Strain into a jar and save in the fridge to use later. Use on fries, mix into mashed potato, etc.
Duck fat is expensive, so worth saving.

One compromise between cutting it up and leaving it whole is spatch-cocking, cutting the backbone out and flattening it open. That's a really good option, one I've used a lot. It cooks more evenly. You can cut it up, but then really, the breast pieces and the legs should be treated differently, and that's maybe more of a lesson than you need when you've never tasted duck. Breath slow, and know that you're in for a treat. (And yes, if it seems rubbery, cook it longer.)

I thought about cutting it up, but decided to roast it whole. So if it's tough after 4 hrs, I should leave it in the oven a while longer? I've never even had duck, so I don't know what I am shooting for, texture wise

The slow approach is best, either starting with a high temp and turning it down, or first roasting low and slow, then giving it a boost at the end, if needed, to brown and crisp it up. I'd guess that most of us who cook duck often treat the breasts and legs separately. But sometimes you want the presentation of a whole duck. Don't be scared! The most important thing to know is that if it's tough, you just have to continue that low-temp roasting.

You might like to read this "Roast Duck 101" from Martha Stewart. It's a higher temperature approach but has helpful tips on how to do it well.
http://www.marthastewart.com/907162/roast-duck-101

Merrill's technique for slow-roasting duck is fantastic: http://www.food52.com/recipes/9115_slow_roast_duck