1) I think at a minimum you should be aiming to get a 2.1, and if possible, a first
Just to make you stand out from the crowd really when it comes to the jobs market (obviously you need more than just a degree these days, but it's always best to give yourself the best possible assets...) - obviously if you cant achieve these then you cant, but there is no harm in trying and really pushing yourself.
2) I'd say it is as difficult as you make it for yourself - which leads me onto the next bit of the question, you make it easier for yourself by doing plenty of reading around your subjects, to broaden your understanding and give you material to use in exams. Good organisational skills and planning is essential here though, as you need to be able to set yourself targets for things to do, and be disciplined enough to get them done. This is especially true around exams, when you need to be doing as many practice essays, or at a minimum essay plans, as you can - and DONT FORGET to memorise specific authors with specific subjects. Believe me... you feel like such an idiot in an exam when you've done the reading for a topic, want to mention an author, but for the life of you you can't remember their name...
3) Couple more tips... use your tutors if you are stuck - could be on anything to do with the material, but if you're stuck just go and ask - you are paying for their service after all, so feel free to badger them, pester them and so on (albeit in a polite way) when it comes to your course if you're stuck. Furthermore, when you get bits of coursework back with their marks, and you notice a mistake in marking, or just plain think you should have got better, dont be afraid to challenge them on it and get it looked at again - it wont kill you or them
To give an e.g. from my own experience again, in my first year I got a piece of Cwork back in which it was specified that we should have used the Uni's search thing when looking for books - I had and had provided screenshots to boot, but somehow my teacher/marker missed them and marked me down - I read the comments, gave it back to him, got it remarked and my grades went up... yeah, sometimes it pays to get it checked...
Other than that all I can say is enjoy your time studying history