You need to have at least 100 Smithing - once you've leveled the skill up that far, you can then use potions and spells to increase it beyond that to a maximum of 255.
I have to agree. I like pretty much everything about Skyrim more, except that the guild questlines in Skyrim weren't quite as good as Oblivion's, IMO. Might just be nostalgia talking there.
Which is understandable. Bethesda's goal from the start was to take Oblivion and improve everything to do with it.
The main gripe I have is the lack of different climates like ES3 and 4 had. Once the lands are fully recreated that won't be a problem. Other than that it's far better than 4.