Wow a lot of professional photographers here, that's a guess but by their response they must be awfuly good!
If you choose a Nikon or Canon, both are solid choices and both can take great photo's. With DSLR's it's really the glass that makes the photo's and the body separate enity. Both Nikon and Canon have great lens and if you can afford their len's you will be happy. There are other players in the lens game, Tamron, Sigma etc .. they are good lens just not the best.
Ask yourself what you will use the camera for. Family, sports, reef, portraits, you get the idea, the broader your needs, will determine how many lens you will need.
The sensor is important, the larger it is the more you can do with the pictures after the fact. Canon mostly uses CMOS sensors and Nikon mostly uses CCD sensors, but I believe Nikon is now using CMOS and CCD in their camera's. The size of the sensor is like the size of the film, the bigger the more you can manipulate the end picture and the more the camera body will cost. Camera's with full size sensors start around $1300 body only. If you plan on using Photo Shop it can help you with the picture manipulating, but it also takes a while too master or even use really. There are other software's out there that are more simple to use.
Learning how to use your new camera can be fun or frustrating depending on your patient level. Personally I would not be overly concerned with the amount of photo's you can take before the camera breaks, most likley you won't go over the hypothetical number.
It's a lot of fun to use a DSLR camera and you are correct, start with the Auto feature and move on from there.
Good luck in your purchase.
