The MP debate is a bunch of bullshit up to a point.

No you won't be shooting bus sides with an 8mp without some pixel stretching but you can shoot commercial easily with it. I still shoot on a 10d and have been printed full page, half, 3/4 and 1/4 as well as cover and advertisement placement easily enough...and technically the 10d was outdated a year after I bought it If you let it limit you then it will always limit you as there is always a bigger MP count available and until you start shooting medium and large format digital you will always be "too small". Learn with what you can afford and progress from there, you may find it is all you really need unti it wears out.

You should be able to go into the menu and get a shutter count (forget the correct name right now) but it will give you an indication as to how much it has been used and when you may need certain servicings such as shutter repair (they wear out once in a while but rarer as time and technology advances). A lot of people buy too much camera when all they really wanted was a P+S so sometimes you can score a 1000 click camera for a smoking deal just because they can't use it anymore.