Peter, just to answer your questions (I know Mick has already covered most of them. I'll just say how it was for me)
what is the exam like? (really easy, multiple choice?)
Personally, I found it rather easy. Like Mick said, the careless, reckless and excessive force was probably the hardest part of the exam - just because they cannot tell you how to look for it. The easiest bit was probably the equipment. The camera would look along a body, and stop at a certain point. It would then zoom into what was wrong - pretty idiot proof. You then get the "Oh, there it is!" from everyone, which helps you along nonetheless!
Secondly:
How is the practical assessed and is it easy to pass?
What bit do you mean? The practical bit on the course? If this is so, you won't be 'assessed'. Your tutor will go through some signals with you, and you will repeat them. Then when I did my course we went into a game with each of us taking turns in refereeing and being assistants. For me I found this harder than the actual game; people were doing small things to try and catch you out. Nothing like what you would encounter in the everyday football on a Sunday!
On the other hand, if you mean the 6 games. None of them will be assessed. You will put your 6 game record down on a sheet and send it off. The assessors have more important games to be assessing, than a newly qualified referee's first couple of games. Your mentor may come along to watch and they may give you some advice, but you will not be assessed on these!
Finally:
and when i become a referee, I was looking for some advice because im scared i might make some wrong decisions?
Ever seen the clip of Graham Poll giving out 3 yellow cards? Even still, have you seen a game of football?! If you have then you are bound to have seen a wrong decision! The problem is not making the bad decision, it is how you deal with it. If you decide to get a flustered and change your mind 100 times. The players will feel unconfident about you - and may try to take advantage too! If you make a bad decision, that is it. It has happened. You can change your mind, as long as play has not resumed. One last thing, is stick by your decision no matter what you say. Don't change it because one set of players are unhappy with the decision!
Good luck in your exam!