1.) no monitor / mouse / keyboard are bundled to the Mac mini, you need to buy it yourself
2.) any mon that has VGA/DVI is ok.
3.) sure, but you will have the best feeling if you use an original Apple keyboard (or any Keyboard claims that the layout is same as Apple's one)
If not, the command key and option key's position will be changed in the normal keyboard, which is not very user-friendly to the Mac OS