According to Todd Howard(Executive Producer on Skyrim) the whole game will take about 400 hours to finish every quest, while the main can be completed in as little as 40 hours. As for the dragons there will be about 20 or so in the game and there are both scripted and dynamic encounters, and you absorb the dragons soul to be used on dragon shouts(very powerful abilities). But they don't appear until a certain quest is done otherwise it would just be unfair to people who don't want to do the main storyline.
Now that's over, on your last point about the game for a warrior from nothing, you could try out Mount & Blade as that is exactly what that game does.
I thought he said 300?