it doesn't really matter
The great thing about Skyrim is that whether it IS too hard or not, if you're having trouble with it, you can just go do something else. I remember on my first ever playthrough (a stealth archer Nord 'King') I got stuck on a mission at level 11 where I had to kill a giant, and just thought nah fuck it and left it. Found the mission later on in the game...40 levels later and went back and killed that bitch with one shot of my mighty uber bow.
Basically - start it and see what you think. The Dawnguard is a lot of fun and the Dragonborn quests have great story lines