Programming for bank

I just wanted to get some advice.

I've had a few years experience in web site design and server-side
programming and am fairly confident in my skills.
There is a local Credit Union wanting to add a few features to their
site (bill pay, transfer money between banks) and I am interested in
the job.

However, I've never worked for a bank before. Any suggestions about
how to win the job, and how to ensure my work is secure enough for this
application would be greatly appreciated. Also, will I have a
liability issue if something goes horribly wrong?

Thanks in advance for you help.

Matthew

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