Yes, you'll be able to play without paying attention to character build, advancement, or online guides. Skyrim has a diverse community of players, from heavy optimisation to deep-immersion roleplayers, and it can attract such a diversity because it easily supports so many ways of playing the game.
It doesn't require character optimisation at all. The game is partially levelled with you, so the challenges are partly tuned to your level. It's not completely levelled with you though (like Oblivion was), so there will be places that are easier or harder depending on whether you're higher or lower level than the area expects. But since the game is non-linear, all that means is that you retreat and go somewhere else instead, and you'll have a hard time running of of things to do elsewhere since the world is pretty wide and deep.
There are quests which do expect a certain level, but those are the exception and the consequence isn't having to go and grind – it's just that you'll do those quests more slowly, or you'll have to wait longer to start them (as in the example of the Daedric quests which have a minimum level before they'll trigger). You certainly won't be stuck with nothing else to do but collect 200 bear pelts to do the next thing or something like that.
The one place where you might get stuck low on coin, depending on how you play, is when it comes to affording a house. A house is very convenient, but it's by no means required to advance. Once you find that you want a house you just start saving your septims instead of spending them all on potion ingredients or what have you, and you'll have enough before long.
Affording a house is the only time I ever felt like I needed to pay attention to managing my character. Otherwise, I'm like you – I go where I like, fight the fights I can and retreat (or often enough, reload a recent save – save often!) from the ones I can't, explore, get immersed in quests, do some in-my-head roleplaying, get to know my character and their opinions of events in Skyrim, and just... y'know, play the game. I've never had any interest in grinding in RPGs, and that's one of the reasons I've fallen in love with the Elder Scrolls games: they let me play how I like to play, whether that's casual, immersive, optimising, grinding, or whatever.
Best Answer
You can get steel crossbows from members of the Dawnguard. You can get the ability to craft dwarven crossbows and the enhanced versions of both crossbow types by joining Dawnguard and doing the Ancient Technology quests. You cannot get crossbows without the Dawnguard DLC or installing a third-party mod to the same effect.