I'm applying for a graduate library trainee position: any advice/pointers?

[Arrghus]

I've completed most of my application (it's to be submitted by the end of the week), and I'm stuck on the part where they ask for a personal statement from you (basically the bit where you're supposed to sell yourself, and tell them why you're better than the rest applying).

I'm a recent Religious Studies graduate, with a first class honours degree. I have rather mediocre GCSEs (not even a C in Maths - I was young and naive and didn't take school seriously, once upon a time), but I pulled my socks up and finally I feel like I've achieved something. But now I'm scared. I am torn between a career in librarianship and information management, and lecturing about the subject I love: namely, that academically manufactured concept of 'Religion' (lower case and upper case!).

I can't afford to do a Master's course (even if I could get a scholarship to cover most of my fees, I'm both too late to apply, and without the money to pay for living costs), so this graduate position appeals to me. It's at a urban university which doesn't offer undergraduate or postgraduate courses in my read discipline. This doesn't bother me, as I really just want to earn some money in a job that doesn't involve working in a shop, or selling things over the phone. I am interested in this work, potentially, and so I also see this position as an opportunity to see if working in a library is for me. Problem is, I don't think my potential employer would want me using their graduate position as a 'testing ground' for my future career.

I am passionate about books, about learning, about academia in general. I am also a bit of a technology enthusiast, which I think helps when libraries are constantly having to evolve in this so-called 'digital age'. I think at an interview I will be able to demonstrate this enthusiasm; my problem here lies with putting it into words!

How much should I write? Are they interested in my passions, or are they more interested in whether I can fulfil the job criteria?

Has anybody got any experience in a similar role? Any sage words?

(Sorry this post is a little lengthy. If you have read this far, I thank you. I'll thank you even more if you can offer some words of wisdom!)