shooting my first formal function - am i ready?

Well yesterday i was offered the chance to shoot a formal dinner/dance at a local hotel school. Ive never done that kind of thing and it is tomorrow so im a little nervous. I was wondering if i would be ok equipment wise. I have a 430ex that i can use with either ettl cord or manually with a wireless trigger, a multifunciontal shootthough/reflective umbrella setup for the formal photos and a 50mm 1.8 II incase i wanna try some natural light shots. Need I be stressing?

How "good" are you at -
1)Positioning the umbrella
2)Setting the ISO and aperture on the camera
3)Setting the flash power on the flash
4)Making sure that (2) and (3) give you a good exposure?

do you mean the iso and aperture on the camera. i've read on the strobist blogs he sometimes mentions dialing in the fstop on the flash but as far as i know you can only set the power and the zoom on the flash so im confused.
i find that shooting with everything on manual i can always get a decent exposure after a few test shots.. and assuming the lighting stays constant. the event will be indoors so i think i can get by on manual. i think im ok with the umbrella too. my main concern is that i wont have enough light.. but in my oppinion i can do small group shots with just one shoot through umbrella. am i right?
i also have a full range of gels should i need them..

Oops, I edited my post above. You are correct, the ISO and aperture are set on the camera. Sorry about that.

I've shot some decently large groups (~15 people?) with just my 580EXII and a shoot-through umbrella. If you're at 1/1 and you need more power, you can always increase the ISO and/or aperture.

Don't worry about 'not enough light' until (assuming ISO 400) your subjects are out more than 40' and your flash AOV coverage is for a 'normal' lens or WA.

From your confusion, it seems you are running a bit short on familiarity with flash in the situation you described. Getting it right 'after a few test shots' is OK for shooting a series of portraits (all subjects standing same distance from flash), but unless you have ETTL or a good command of flash exposure according to Guide Number arithmetic, at fast paced events with variety of flash distances you will likely flounder. (Those of us who are experienced with flash before Auto flash even existed had developed techniques to deal rapidly even without flash meters...today's shooters would be lost, for the most part, just as so many cannot drive a manual transmission car.)

'Small groups' I presume to refer to 6 people groups? If so, no problem. Larger groups spread over a wider area, the technique of 'feathering' the light on the closest person (to prevent overexposure of that person while also underexposing the farthest person in the group) should be kept in mind.

allow me to provide more detail.. there will be two photographers at the event: one who will stay in the same place taking the formal photos (mostly couples) and one who will walk around the venue and take photos of pretty much anything they want.

as of yet, i dont know which of the two positions i will have but i assume it will be the formal option considering i have some capable equipment. even though im still not a pro at shooting manual, the lighting should be consistant so once i get it right im good to go. if i happen to get the other position, my only option would be to use the ettl cable to get the flash of camera albeit only a foot or two. as far as i know there will be white celiengs and wall which always helps hehe.

Wilt wrote in post #11051478
'Small groups' I presume to refer to 6 people groups? If so, no problem. Larger groups spread over a wider area, the technique of 'feathering' the light on the closest person (to prevent overexposure of that person while also underexposing the farthest person in the group) should be kept in mind.

forgive my ignorance but how would i do that? by simply adjusting the position of the light or is it something else?

The concept of feathering (a softbox) illustrated, but technique can be applied with umbrellas. (I made this illustration many years ago)

thanks for the illustration wilt

everything went well there were a couple big groups of 10 or so people but it went by without any big issues. the 'feathering' technique definitly came in handy. thanks again!
will post some pics up when ive had a chance to import them.