I have a little bit of a problem with the construction of "priez-vous m'aider". It is rather standing it on its head. If you want to use prier I would suggest, "Je vous prie m'aider" ie "I beg you to help me".
The main consideration, no matter whom you are dealing with, fonctionnaire, shop assistant etc, it is always wise to start with "Bonjour". It isn't necessarily considered rude in UK to address a question without preamble and relying on tone and inflection but not so in France.
All above IMHO
BTW this isn't really my second post. I was a contributor previously but a change of email address and forgotten password meant I ended up rejoining.