Yea I've done this several times before, though i've always used the original Thompson model that is used in x-box. This website sells every stock x-box part, as well as a bunch of upgrades:
http://www.llamma.com/xbox/Repairs/repairs.htm
Go to 'Parts in Stock' then go to 'Major XBox Parts' and scroll down a bit. They sell original Thompson DVD drives for 49 dollars a pop.
It is pretty easy to swap them. About the hardest thing is getting the x-box lid back on if you leave the metal heatshield on. That thing is a bitch...it gets hung up on EVERYTHING. I found it impossible to put the lid back on without taking the heat shield off. My X-box has been without the heat shield for over a year now and has had no problems, so it's not a big deal.
It is possible to upgrade your DVD drive with a better model, but if I remember correctly, you need to either do somethign to your hard drive to get the correct drivers onto it, or you need a modchip. This is a website I used to visit frequently when I was into modding my x-box (all I did was cosmetic and electrical mods), and they have a ton of tutorials for everything from installing a modchip to changing the color of the power LEDs. They have a bunch for updating your DVD drive if you want to:
http://www.xbox-scene.com/