read up on texture mapping if you haven't already
you'd just assign a new material and in the colour slider you click the little checkered box and hit file from the dialog that appears. although, you need to have set up your UVs for anything to show up the way you want it to

second question: yes.
i don't remember how, but there is a free video tutorial on this site. go look for it

i would give you the links to such things but you can easily find it