Avoid them for now. The cube is actually in the main area as soon as you enter the ruins, so you didn't actually need to explore the lower levels yet. When you get all the way to the bottom [of the main room], there's the 3 doors you can go into, but you'll also notice there is a second level above you. There is a bit of a path you can go up on the side to get on top. It's on a desk, if I remember right. Either on the desk, or in it.
There are certain monsters you will run into that will just annihilate you at lower levels (and even higher levels, later on) and you need to recognize them so you can avoid them. Once you've levelled high enough and got better equipment, they won't be much of a hassle anymore. Either that or in the case of the specific monsters you're talking about, you could get some potions to increase your poison resistance or find some magic items that increase your poison resistance and try again.
Oh and Dwemar artifacts sell for a good amount of money. They're illegal, but you can sell them to certain people without problems. The General Trader in Balmora will buy the stuff off you. Also, if the person you're buying off doesn't have full money anymore because you've sold him other stuff, just press the rest key. Since you're standing right in front of him, you can't sleep, but you can just have your character "wait" for a set amount of time. Wait for 24 hours and the merchant will have full money again.
edit: Generally, when something kills you in 1 hit, that means a few things. Usually it's either because you're really weak against that particular type of attack or you don't have a lot of hit points period. The other possibility is that the one particular attack is very strong. I know for a fact the automatons you're talking about aren't terribly strong, so it's probably one of the first two. Get the cube, go back and keep up with the quests. They're a good way to level up at lower levels, but just like the rest of the game you'll notice they put you in areas you can easily die unless you're careful. They won't set you up so you can't beat the quest, but you have to be careful most of the time just to make sure you don't run into something you can't deal with.