I think you might be surprised - most people who estimate how much they might get back tend to find there are much more charges than they thought!
There should be an address listed in the sticky posts at the top of the RBS forums. Otherwise just send to their Customer Relations Team (should be easy to find on RBS website).
They cannot touch your bank account because you are going after your credit card however, the
Ombudsman
would be very keen to hear from you if they made any retaliatory action towards your
overdraft
if you went for your bank account charges (because they can't do that). Something to consider.
As for being scared - be assured that pretty much everyone here was in your boat at one time and with the help and support of those around you (and a bit of research from yourself) you will be a pro in no time.
Spend some time looking through the RBS successes and also the Library forum - there are plenty of FAQs, guides and template letters available in that area that should help you enormously.
Good luck
