Also, there are a few "marks" on the machine, in the four corners of the display. Do these look like I can scrub them away?
These appear to be scratches. The surface coating has been removed to reveal the darker aluminium underneath. Try to remove it and it'll look worse.
Lastly, and frankly what angers me, is the display is slanted when closed. It doesn't close entirely on the right side. What the hell is causing this, and how can I fix it? The seller on eBay NEVER mentioned ANYTHING about this.
It's also a common problem on the 2006/2007 MacBook Pros that share a similar chassis. Either the lid or chassis or both are slightly bent. It's usually the lid because the previous owner was right handed and opened it from the right hand edge rather than the centre.