Answer 1: Yes, stay the fuck away. If Race XYZ has ability to monitor us without us knowing, thus not interfering with us, sure go ahead. Its not like there's much we could to stop them. But the moment they make their existence known, we're fucked.
At that moment, we aren't the world-conquering successful species we love and proclaim to be. We're the little tribe living on the little island that's quietly being protected by the corrupt government of a minor power in the universal state of nations and empires that we just are now learning about. There's a lot of euphemisms in my last few sentences. Figure them out.
Leave these people alone.
This is kind of in response to your second point. Think about the scale of what we're talking about. We have a massively global, interconnected society of both economy and knowledge comprising billions of people. Even the poorest person in the most desolate parts of the world can, with some inconvenience, get on to the Internet. The people on this island, 400-1000 souls that they be, don't even have the understanding of modern society that the poorest person in the modern world has. Where do you start with that?
So suppose your friendly aliens show up and say "Hi!". What then? We're the people that struggle to maintain ONE space station. We have no extra-terrestrial colonies or establishments. Aliens decide to claim Mars? What are we going to do? The Moon? Its theirs. Pretty much anything outside of our little island Earth is open for claim, and not by us necessarily. The fucked up part is that if you traveled tens or hundreds of light years to get here, Earth itself is probably not the main goal. Its just the natural resources of the system. And what happens in a few hundred years when we decide to get off our asses and go into space? Nothing's left, because fucking Zork claimed it all.
So when you think about all of this together, what options do you present to these people even if they were interested? Medicine, food? Sure. Maybe we can get them vaccinated before the common cold or bird flu wipes them out. Education? Here's some books representing external human history from the perspective of the people supplying the money. Oh, check out our religion too! By the way, did you know that your island is one of several others claimed by India? Its a big island (not really) with over 1 billion people. Too many to count? Don't worry, once your 100 kids have moved to Bangalore to become tech support reps and within 20 years your entire culture has died they'll be able to explain.
I know this is a bit rambly, but hopefully you can see where I'm going. There is no benefit to the people in question to be contacted by us. It only changes and hurts them.