Regarding the oil... What you've described matches exactly every K24 I've seen, including our own. There will be varnish on the splash shield directly under the oil fill cap, but if you look around with a flash light into the valvetrain area, you will see that it's very clean.
Here's the bottom side of my cylinder head cover. Lots of discoloration, right?
But the actual cylinder head and valvetrain area are very clean.
Your K24 will look similar to mine with one exception. Your intake camshaft (the front one) will have three lobes per cylinder instead of two lobes like mine has. Your version of the K24 has what is closer to a "power" VTEC implementation where the engine will use the larger cam above about 5,000 rpm (you should hear the changeover). Mine has the "economy" VTEC implementation which is a little different. Yours uses a single cam lobe for both exhaust valves, similar to mine.
Regarding the warranty... In general, the opportunity to negotiate on a warranty is gone once you've driven the car home. The point at which you have a little more leverage is sitting in the finance office, when you haven't actually signed any papers yet. That's where you offer them $500 for a $900 warranty and that's when they'll say, "well, I can only do this a few times a month, but sure, I can do that." Now that you're (presumably) done with the purchase and have already taken the car home, the dealer has much less incentive to offer a better deal on the extended warranty.