When you get a "new" old bike, I'd always give it a thorough once over to check everything.
-As mentioned, that drain tube from the airbox normally has some oil and water in it, and it's SUPPOSED to be emptied at every oil change. I wouldn't be the least bit surprised to find a neglectful PO didn't realize he was supposed to do that. Empty it and carry on.
-Your oil around the clutch cover could simply be over spray. Clean everything thoroughly, go for a ride, and observe.
-Open up your airbox and check out your filter, then determine if you need to replace it. You can also research the "nu-foam" upgrade where you remove the paper element and simply build a less restrictive air filter using the old metal frame.
-It never hurts to change your oil and filter, unless you use the wrong stuff. Go get some oil that's well endowed with ZDDP like Rotella, get a new filter, and install it the right way! If your oil window doesn't clear up, you might try putting some kerosene or diesel in your CRANKCASE after you've drained your oil. Let it soak for a while, and it'll clean things right up. Drain it off before you add your oil, but don't worry; you won't catch fire.
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Manuals are ALWAYS a great thing to have. I've downloaded the clymer's manual, owner's manual, parts manual/diagram... all free, all thanks to this website.