This topic is rather close to home for me.. So allow me to give my thoughts on the matter!
TL:DR -- An intelligent species would easily be able to understand us. That is assuming they are more advanced than we are. If they are at or lower than our own technology, then we'd possibly have an issue in communicating. But advanced civilizations means advanced computing, and to the kind of computations that a civilization just one-hundred years ahead of us has.. our languages are nothing more than absolutely trivial to such a machine
When it comes to evolution, it would seem some are under the mistaken impression that a sort of "guiding force" is directing life ever towards a "higher" state of evolution. Well, that just isn't the case.
Why would an extraterrestrial have a mouth? Well, as in the case here on Earth (which is the only planet on which we know complex life exists, so I'm going to exclude the conjecture of other non-Earth type worlds) we know that evolution will tend towards similar solutions for similar problems. A creature has to eat ya know At least if it wants to have the kinds of energy required to do fast mental computations, it'll need more energy than something that just survives with means other than predating on other life.
With that in mind, if these beings come from a world like ours, it is a safe bet that the five billion years it took Earth to get to us for me to be here today to type this message.. The solutions that were successful here, will likely be just as successful elsewhere. Now that isn't to say that five fingers, two arms, or legs is best for intelligence! However I'd caution against the notion of lots of eyes.. Nature doesn't tend towards excessive! It goes with what works and that's that! Two eyes are AMAZING for getting all the visual information you need to catch your food at great (land) distances. And remember! Excellent hearing or smelling is nice, but sight is at the speed of LIGHT! So it is just a better overall system for "general" information gathering. To catch fast things, gotta see it fast and be fast! As life on Earth will teach you.. if it isn't a fast thing, that typically means it isn't worried about you eating it.. which means you should worry about eating it. But I digress slightly!
What I find most fascinating about the notion of life out there is.. If not DNA, then what? Because when we look out at the chemical makeup in space, man.. It is almost part for part what we're made of! No matter where we look!! It is wild. And if I were a betting man.. I'd say life is pretty much everywhere out there that it can be. There is evidence that life started on the Earth as early as the end of the Hadean period. Like the moment water could be here, boom.. life.
However.. Do not count on life at our um.. "level". Based on how hostile the universe as a whole is, and most of the Earth-type worlds we see out there (in terms of orbit) they are around red dwarf stars. Those things are crazy awesome for long-term survival.. but boy oh boy for the first few billion years, they are mean bastards! We're talking CRAZY plasma storms that would just fry anything biological. Just cooked. I could go on and on about how just unlikely we are to find any other civilizations in our galaxy, that are either alive or even have ever been. The odds just aren't in their favor. But I know, some people will be like "that is your anthropomorphic basis showing" and they'd be right! And wrong! We aren't here because we're special, we're here because this is where we could be We don't live on Mars or Venus for a reason. We simply can't exist there.
Life is complicated, and complicated life is not the directive of life itself.. Keep in mind that our world, our beautiful Earth.. had nothing but slime on it for over three and half billion years. It has had something more interesting than slime for less than a billion years. In a galaxy that is twelve-ish billion years old.. it took almost a third of its lifespan just to get us here, and we've almost died numerous times! Things falling out of the sky, to giant ass volcanoes letting us know just how tiny we are..
Conclusion: Life exists everywhere it can, in whatever form is best suited for that environment! Just don't expect little green men or ET to be out there waiting to greet us when we graduate to the next stage.. Remember.. someone has to be first, and I see no law in physics that dictates we aren't the ones that will take on the mantle of Elders in the vast cosmos. Or, we're in a zoo and the aliens are being overly secretive with their existence. This is my opinion, take it for whatever worth you find in it.