Ted Hooper, my bee keeping bible, yes I have the book too :-)
to note: guard bees will often let other bees in if they carry nectar or pollen with them, even if they are not of that hive.
Try to get in empty handed.......don't!!!! an all out attack will follow.
I like to think that what I can smell is the romance of the hive, soft and warm - my girls!

ok, so you can get stung, and ouch it does flipp'in hurt, but hey ho! thats the way of it :-)

TGR- you will make a great beekeeper, of this I am sure. The bees left to their own are really good at looking after themselves, even in a hive. So, there is not much to go really wrong- the worst thing are the nasty diseases that are about these days, your local bee inspector can help with advice and checking you hive for you. Don't let this put you off, Swarming is one other little thing to try and curb if you have people living/working near your hive.
Try and get on a course, and become a much needed beekeeper.