The easiest way to give the bore a quick view is to open the action, and insert some light colored paper, then find a good light. This will shine enough light down the barrel that you can see plenty of detail.
Surface rust may not be a horrible thing-I've de-rusted several guns, and found them to be excellent. Again, the question is neglect, or abuse. From your description, it could go either way. I would certainly use the condition and appearance to horse trade a little on that price.
